A review of cryogenic cooling in machining processes.pdf

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International Journal of Machine Tools & Manufacture 48 (2008) 947964

A review of cryogenic cooling in machining processes

Yakup Yildiz, Muammer Nalbant

Department of Mechanical Education, Faculty of Technical Education, Gazi University, Ankara, Turkey

Received 1 May 2007; received in revised form 7 January 2008; accepted 21 January 2008

Available online 3 February 2008

Abstract

The cooling applications in machining operations play a very important role and many operations cannot be carried out efficiently

without cooling. Application of a coolant in a cutting process can increase tool life and dimensional accuracy, decrease cuttingtemperatures, surface roughness and the amount of power consumed in a metal cutting process and thus improve the productivity. In this

review, liquid nitrogen, as a cryogenic coolant, was investigated in detail in terms of application methods in material removal operations

and its effects on cutting tool and workpiece material properties, cutting temperature, tool wear/life, surface roughness and dimensional

deviation, friction and cutting forces. As a result, cryogenic cooling has been determined as one of the most favourable method for

material cutting operations due to being capable of considerable improvement in tool life and surface finish through reduction in tool

wear through control of machining temperature desirably at the cutting zone.

r 2008 Elsevier Ltd. All rights reserved.

Keywords: Cryogenic cooling; Liquid nitrogen; Machining processes; Tool life; Surface roughness

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 948

1.1. Cutting fluids (coolants) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 948

2. Cryogenic cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 949

2.1. Heat generation in machining process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 949

2.1.1. Temperature distribution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 950

3. Cryogenic cooling approaches. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 951

3.1. Cryogenic pre-cooling the workpiece. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 951

3.2. Indirect cryogenic cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 952

3.3. Cryogenic spraying and jet cooling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 952

3.4. Cryogenic treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 953

4. Miscellaneous effects of the cryogenic cooling in machining processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 953

4.1. The effect of cryogenic temperature on material properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 953

4.2. The effect of cryogenic cooling on cutting temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 954

4.3. The effect of cryogenic cooling on tool wear and tool life. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 955

4.4. The effect of cryogenic cooling on surface roughness and dimensional deviation. . . . . . . . . . . . . . . . . . . . . . . . . . . 957

4.5. The effect of cryogenic cooling on friction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 958

4.6. The effect of cryogenic cooling on cutting forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 959

5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 961

Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 962

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 962

ARTICLE IN PRESS

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Corresponding author. Tel.: +903122 028686; fax: +903122 220059.

E-mail address: [email protected] (Y. Yildiz).
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1. Introduction

Excessive heat and consequently wear formation are the

most important factors affecting performance and produc-

tivity of metal cutting operations. Different methods,

i.e. hot machining [1], high-pressure coolant application

[2], application of minimum quantity lubrication (MQL)[3]have been tried by researchers to enhance machining

performance. One of these methods is conventional cutting

fluid application.

1.1. Cutting fluids (coolants)

Conventional cutting fluids were classified into three

groups as seen in Fig. 1 [4]. Water soluble fluids were

defined suitable for operations where cutting speeds were

very high and pressures on the tool were relatively low.

Neat cutting oils are straight mineral oils, or mineral oils

with additives. They were preferred when cutting pressures

between chip and tool face were very high and where the

primary consideration was lubrication. It was determined

that cutting fluids cannot penetrate the chiptool interface

at high-cutting speeds [5]. Gaseous lubricants were seen

very attractive when the cutting fluid penetration problem

was considered but the high cost of gases made them

uneconomical for production applications.

The purpose of the application of the cutting fluids in

metal cutting was stated as reducing cutting temperature by

cooling and friction between the tool, chip and workpiece

by lubrication [6]. Chip formation and curl, which affects

the size of the crater wear and the strength of the cutting

tool edge, is also affected when coolant is carried outduring machining. Generally, a reduction in temperature

results in a decrease in wear rate and an increase in tool life.

However, a reduction in the temperature of the workpiece

can increase its shear stress, so that the cutting force

may be increased and this can lead to a decrease in tool

life [7]. For instance, Seah et al. examined water-soluble

lubricating on tool wear in turning of AISI 4340 and AISI

1045 steel with an uncoated tungsten carbide insert. They

found that there was no significant difference between the

cases where coolant was used and that of dry cutting. In

fact, they showed that it aggravated flank and crater wear

in some of the cutting conditions [8]. It was also proved

that the conventional cooling action worsened the surfaceroughness when compared with dry cutting [9].

On the other hand, applications of conventional cutting

fluids in industry create several health and environmental

problems[10,11]. Environmental pollution due to chemical

dissociation/breakdown of the cutting fluid at high-cutting

temperature; water pollution and soil contamination

during their ultimate disposal; biological (dermatological)

ailments to operators health coming in fumes, smoke,

physical contact, bacteria and odours with cutting fluid;

requirement of extra floor space and additional systems

for pumping, storage, filtration, recycling, chilling, etc.

According to the statistical data of 2002, total environ-

mental expenditure of Turkey was $402,947,766. There

were 272,482 firms in manufacturing industry for the same

year[12]. If each of these firms had one machine (lathe or

mill) and if each of these machines held 100 L of cutting

fluid, tons of waste cutting fluid must have released to

environment.

So, it is absolutely necessary to use an environmentally

acceptable coolant in manufacturing industry. For this

purpose, liquid nitrogen as a cryogenic coolant has been

explored since the 1950s in metal cutting industry.

However, it was not examined entirely at the beginning

due to the high costs associated with early cryogenic

technology. Uehara and Kumagais studies [13,14] havepioneered to todays cryo-machining works. Their experi-

mental findings were considerable in terms of machining

performance. The subject has been still studied in different

views and gaining interest due to its remarkable success on

machinability. From the machining tests and cost analysis

in a study [15], the following advantages of cryogenic

ARTICLE IN PRESS

Fig. 1. Classification of cutting fluids.

Y. Yildiz, M. Nalbant / International Journal of Machine Tools & Manufacture 48 (2008) 947964948


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cooling over conventional emulsion cooling were deter-

mined such as longer tool life, better chip breaking and

chip handling, higher productivity, lower productivity cost,

better work surface finish, environmentally safer, healthier

for the worker. For instance, when compared with

conventional emulsion cooling, cryogenic machining had

productivity gains of up to 21.36% in machining of AISI

304 stainless steel for different speeds as seen in Fig. 2.

In this study, cryogenic cooling application methods and

their effects on production in machining operations have

been reviewed in detail. Most of cryogenic cooling

applications in machining studies have been examined in

turning operations even though there were its applicationsin other machining operations such as grinding [1619],

drilling [20] and milling [2123]. Contrary to turning

operations, cryogenic cooling has been investigated less

by the researchers in milling operations due to possibility

of thermal cracks on cutting tool in intermittent cutting

operations and difficulties in practice. However, excep-

tional improvements over dry cutting and emulsion cooling

were achieved with cryogenic cooling by Hong et al. in

milling processes[24,25]. For example, in milling of A390

with high-speed steel cutting tools, the tool life ratio over

dry cutting was found bigger than 1000% by cryogenic

cooling.

2. Cryogenic cooling

Cryogenics express study and use of materials at very

low temperatures, below 150 1C. However, normal

boiling points of permanent gases such as helium,

hydrogen, neon, nitrogen, oxygen, normal air as cryogens

lie below 180 1C. Cryogenic gases have a wide variety of

applications in industry such as health, electronics,

manufacturing, automotive and aerospace industry parti-

cularly for cooling purposes. Liquid nitrogen is the most

commonly used element in cryogenics. It is produced

industrially by fractional distillation of liquid air and is

often referred to by the abbreviation, LN2. Nitrogen melts

at 210.01 1C and boils at 198.79 1C, it is the most

abundant gas, composes about four-fifths (78.03%) by

volume of the atmosphere. It is a colourless, odourless,

tasteless and non-toxic gas[26,27]. These characteristics of

liquid nitrogen have made it as a preferred coolant [15].

The main functions of cryogenic cooling in metal cuttingwere defined by Hong and Zhao [28] as removing heat

effectively from the cutting zone, hence lowering cutting

temperatures, modifying the frictional characteristics

at the tool/chip interfaces, changing the properties of

the workpiece and the tool material. So, it will be useful

to summarise heat generation and temperature distribu-

tion in a machining process for better evaluation of the

subject.

2.1. Heat generation in machining process

In any machining process, heat is generated as a result ofthe plastic deformation of the layer being cut and

overcoming friction on the toolchip and toolwork

interfaces. This heat is dissipated by the four systems in

processing the material such as the cutting tool, the

workpiece, the chip formed and the cutting fluid. The

greater part of the heat passes into the chip, while a

proportion is conducted into the work material. This

proportion may be higher for low rates of metal removal

and small shear zone angles, but the proportion is small for

high rates of metal removal [29]. OSullivan and Cotterell

measured machined surface temperature using thermocou-

ples in turning of aluminium alloy 6082-T6 with carbide

inserts and their test results indicated that an increase incutting speed resulted in a decrease in machined surface

temperatures. This reduction was attributed to the higher

metal removal rate which resulted in more heat being

carried away by the chip and thus less heat being

conducted into the workpiece[30].

The main regions where heat is generated during the

orthogonal cutting process are shown in Fig. 3 [31].

Majumdar et al. developed a finite element-based compu-

tational model to determine the temperature distribution in

a metal cutting process. Same temperature distribution was

proved by their model and they indicated the maximum

ARTICLE IN PRESS

Fig. 2. Comparison of production cost and productivity of cryogenic

machining with emulsion cooling [60].

Fig. 3. Heat generation zones in orthogonal cutting [31].

Y. Yildiz, M. Nalbant / International Journal of Machine Tools & Manufacture 48 (2008) 947964 949


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temperature generation at the toolchip interface [32].

Aspinwall and co-workers employed infrared pyrometer

and FE model as direct and indirect techniques to measure

cutting temperatures in turning of hardened hot work die

steel and AISI H13 with PCBN (polycrystalline cubic

boron nitride) tool. They obtained good correlation

between two techniques and their model also predictedthe highest temperatures at the toolchip interface[33].

Heat generation and temperatures in the primary and

secondary zones are dependent on a combination of the

physical and chemical properties of the workpiece material

and cutting tool material, highly cutting conditions, the

cutting speed, the feed rate, the depth of cut, and less the

cutting tool geometry and the cutting fluid[31]. When low-

alloy engineering steel was machined with cemented

carbide tool, it was seen that cutting temperature increased

with increasing of cutting speed and feed rate. In addition,

the effect of air and water as a coolant decreased while the

cutting speed increased [34]. The other factor affecting

the cutting tool temperature is the contact length between

the chip and the tool, and it was determined that the

temperature was increased with the contact length for the

orthogonal cutting of aluminium[29].

2.1.1. Temperature distribution

Komanduri and Hou [35] examined the temperature

distribution due to the combined effect of shear plane heat

source in the primary shear zone and frictional heat source

at the toolchip interface in metal cutting. They applied a

model developed by them to conventional machining of

steel with a carbide tool and aluminium with a single-crystal diamond benefiting from data obtained by different

researchers. They validated the model by comparing

analytical results with the experimental results. Fig. 4

shows temperature distribution according to their model.

While the maximum temperature rise at the toolchip

interface located farther away from the tool tip in the case

of machining steel, it was nearer to the tool tip in

machining of aluminium. This case was attributed to the

differences in the thermal properties of the tool, the work

materials and cutting conditions.

Ay and Yang performed an experimental study to

monitor temperature variations of the tool and workpiece

in orthogonal cutting using both thermocouples and

infrared thermovision. They used uncoated carbide inserts

as cutting tool and cast iron, AISI 1045 steel, copper and

6061 aluminium as workpiece material. Fig. 5 shows their

ARTICLE IN PRESS

Fig. 4. Isotherms of the temperature rise in the chip, the tool and the work material: (a) conventional machining of steel with carbide tool, (b) machining

of aluminium with a single-crystal diamond tool [35].

Fig. 5. Temperature distribution: (a) rake face, (b) flank face[36].



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temperature distribution by combining the results from the

infrared and thermocouple tests for cutting AISI 1045 steel.

The maximum temperature was found on the rake face of

the tool[36].

According to metallographic techniques and changes in

the hardness of the tool, the maximum temperature on the

rake face on the tool is remote from the cutting edge. Thishappens for many materials and cutting conditions, but it

can be a difference for some materials as seen inFig. 6due

to ductility of the material. These distributions of

temperature have been explained in terms of the seizure

zone of the cutting tool interface [29].

The studies cited above verified that the maximum heat

generation in a machining process is at the toolchip

interface on the rake face of the tool. The most important

tool failures such as flank wear on main and auxiliary

cutting edge, crater wear on rake face and BUE formation

occur around this zone of the tool [37,38]as seen in Fig. 7

[39]. For example, in high-speed face milling of tempered

steel using an Al2O3-based ceramic tool and cemented

carbide tool, it was seen that high temperatures caused

crater wear formation on the rake face of the tool [40].

Same conclusions were also observed in turning of AISI

1040 steel with ceramic tools [41]. Consequently, an

efficient coolant application intending to cool toolchip

interface around the rake face of the tool would be the

most efficient particularly to impede heat generation. For

example, Wang and Petrescu [42] made stress analyses of

CBN insert in machining of RBSN ceramic using a

cryogenic coolant. They found that a decrease in tempera-

ture by cryogenic cooling caused an important reduction in

stress at the flank face of the cutting tool without a crack.Another study [43] showed that when the ferrous metals

were machined with natural diamond tools under cryogenic

cooling condition, tool wear were controlled effectively,

which means that the possibility of the diffusion and

adhesion were reduced. Evans [44] similarly turned the

stainless steel with diamond tools by cryogenically and he

obtained good surface finish. In another study [45], 52100

bearing steel, A2 tool steel and WC-Co rolls were

machined with alumina ceramic (Al2O3), PCBN and

polycrystalline diamond (PCD) tools under cryogenic

cooling conditions. Significant tool life improvements in

cryomachining of such hard ferrous materials were

attributed to more efficient heat removal from the cutting

insert and reduction in thermal softening of the cutting

tools at higher temperatures.

3. Cryogenic cooling approaches

Cryogenic cooling approaches in material machining

could be classified into four groups according to applica-tions of the researchers: cryogenic pre-cooling the work-

piece by repulsing or an enclosed bath and cryogenic

chip cooling, indirect cryogenic cooling or cryogenic tool

back cooling or conductive remote cooling, cryogenic jet

cooling by injection of cryogen to the cutting zone by

general flooding or to the cutting tool edges or faces,

toolchip and toolwork interfaces by micro-nozzles,

cryogenic treatment of cutting tools to enhance their

performance can be assumed another group executed by

the researchers.

3.1. Cryogenic pre-cooling the workpiece

In cryogenic pre-cooling, the workpiece and chip

cooling method, the aim is to cool workpiece or chip to

change properties of material from ductile to brittle

because, the ductile chip material can become brittle

when the chip temperature is lowered [46]. Chip formation

and its effect on productivity in metal cutting have been

ARTICLE IN PRESS

Fig. 7. Diagram of worn cutting tool, showing the principal locations andtypes of wear that occur [39].

Fig. 6. (a) Distribution of temperature on the rake face of a tool, (b) distribution of temperature on the rake face of the tool when cutting high-

conductivity copper[29].



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proved by Jawahir [47] and control and breaking of chips

during cutting will increase performance of machining.

This method was also attempted to freeze the workpiece by

cryogenic enclosed bath or general flooding. A sample

study was made by Bhattacharyya et al. [48]and they tested

two methods; in first method, they dipped the test rod in

liquid nitrogen and in second method, they poured theliquid nitrogen by continually onto the testpiece. Another

sample practice was also experimented by Ding and Hong

[49]. Their test setup was illustrated inFig. 8. They gained

significant improvement in chip breaking with pre-cooling

of the AISI 1008 low carbon steel. Hong et al. [46,50]also

developed a cryogen delivery system as seen in Fig. 9. In

this system, LN2 was supplied to chip faces to improve the

chip breakability. In this design, the size, shape and

position of the nozzle were selected so that the LN2 jet

covered the chip arc, and liquid flow was oriented parallel

to the axial line of the curved chip faces. They proved in FE

analysis that their method provided embrittlement tem-

perature of chips, below

55 1C, for the AISI 1008. In a

design of Ahmed et al. [51], the gas flow was directed

towards the tool cutting edge to cool the newly generated

chips and enhance their brittleness.

However, these methods may be impractical in the

production line and negatively increase the cutting

force and the abrasion, in addition, they can cause

dimensional change of the workpiece and, particularly

high liquid nitrogen consumption can be required un-

economically[52].

3.2. Indirect cryogenic cooling

This method was also called as cryogenic tool back

cooling and conductive remote cooling. In this distinctive

cryogenic cooling approach, the aim is to cool the cutting

point through heat conduction from a LN2 chamber

located at the tool face or the tool holder. In other words,LN2 is not repulsed to the tool or workpiece. An example

was described by Evans [44]; he cooled the tools by

immersing the tool shank in reservoir of liquid nitrogen.

But his system was not suitable for a practical machining

process. Fig. 10 illustrates an alternative application of

LN2 to a chamber between the tool insert and shim to

freeze the tool back face [53]. Similarly, Wang and

Rajurkar [5456] designed a liquid nitrogen circulation

system on the tool for conductive cooling of the cutting

edge. Ahmed et al. [51] modified a tool holder with two

designs for cryogenic machining. In one of their design, the

discharging gas was directed away from the workpiece for

maintaining ductility of materials. Piling up of nitrogen

below the insert and thus keeping the tool insert at low

temperatures were targeted without evaporating. So, the

design is suitable for conductive remote cooling of the

cutting edge.

The machining performance could be improved by

indirect cryogenic cooling method because the cooling is

restricted only to the cutting insert, LN2 does not contact

with the workpiece and it does not cause significant change

in properties of the workpiece, in addition, cooling effect is

stable [55,56]. However, the effect of this approach is

highly dependent on thermal conductivity of the cutting

tool material, the distance from the LN2 source to thehighest temperature point at the cutting edge and insert

thickness. It can be more effective if a larger area of the

tool insert is in contact with LN2 [53].

3.3. Cryogenic spraying and jet cooling

The objective in this method is to cool cutting zone,

particularly toolchip interface with liquid nitrogen by

using nozzles. LN2 consumption and thus production cost

could be high by general flooding or spraying of the

coolant to the general cutting area in a machining

ARTICLE IN PRESS

Fig. 9. LN2 delivery system for chipbreaking tests[50]. Fig. 10. Application of LN2 to tool back[53].

Fig. 8. Cryogenic workpiece pre-cooling[53].



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operation. Fig. 11 illustrates such a cryogenic supply

system developed by Zurecki et al. [57]. In such an

application, coolant can also lead to cooling unwanted

areas and increasing of the cutting forces [58].

Alternatively in a cryogenic jet cooling method, LN2 is

applied with micro-nozzles to the tool rake and/or the tool

flank, where the material is cut and maximum temperatureis formed[15].Fig. 12shows an example device developed

by Hong [59] for turning operations. In such an LN2

delivery nozzle system, a flat cutting insert is used with an

additional chipbreaker and LN2 is sprayed through a

nozzle between the chipbreaker and the rake face of the

tool insert. The chipbreaker helps to lift up the chips and so

that LN2 can reach the toolchip interface. In another

design of Hong and Broomer, LN2 was injected with three

nozzles to the cutting zone; in a Zdirection, parallel to

the spindle axis, or in Xdirection, perpendicular to the

spindle axis, on the tool rake face and flank face, similarly

[60]. In design of Dhar et al. [6163], LN2 jets were

targeted along the rake and flank surfaces, parallel to the

main and auxiliary cutting edges too. In another design,

Venugopal et al.[64]used LN2 jets through a nozzle on the

face and flank of the cutting tool.

There are distinct advantages of the cryogenic jet

cooling. The cooling power is not wasted on any unneces-

sary areas and thus, workpiece will constant temperature

and not subject to dimensional inaccuracy and geometrical

distortion; this localised cryogenic cooling reduces the tool

face temperature, enhances its hardness, and so reduces

its wear rate; this approach also embrittles the chip by

cold temperature and bend the chip with the chipbreaker.

This cryogenic machining approach eliminates the BUE

problem on tools because the cold temperature reduces the

possibility of chips welding to the tool and the high-

pressure cryogenic jet also helps to remove possible BUE

formation, therefore it will produce better surface quality

[15]. In addition, LN2 cannot be circulated inside the

machine tool like the conventional cooling fluids, as LN2 is

released into normal atmospheric pressure and absorbsheat during the cutting process; it quickly evaporates [53].

In this method, the nitrogen consumption can be so small,

for instance, volumetric LN2 flow rate was measured as

0.625 L/min for rake nozzle, 0.53 L/min for flank nozzle

and 0.814 L/min for both rake and flank nozzles [65]. So,

this process can improve the productivity and reduce the

production cost significantly[66].

3.4. Cryogenic treatment

Cryogenic treatment is a process similar to heat

treatment. In this method, samples are cooled down to

cryogenic temperature and maintained at this temperature

for a long time and then heated back to room temperature

to improve wear resistance and dimensional stability of

them [67,68]. For example, Yong et al. [69] performed a

treatment method of tools cryogenically as follows: inserts

are placed in a chamber; temperature is gradually lowered

over a period of 6 h from room temperature to about

184 1C; temperature is then held steady for about 18 h;

temperature is gradually raised over a period of 6 h to

room temperature and inserts are tempered. Steps followed

by Silva et al. [70]for the cryogenic treatment were: tools

were conventionally quenched and tempered lasting a total

of 43h; cooling to

196 1C (20 h); heating to +196 1C(8 h); hot stabilisation at +196 1C (2 h); cooling to room

temperature (1 h); stabilisation at room temperature (2 h);

heating to +196 1C (1 h). These steps were repeated three

times.

There are a lot of applications of cryogenic treatment or

processing to enhance wear resistance and strength of tool

materials from end mills to guillotine knives in industry

[71]. However, the effect of the cryogenic treatment on

cutting performance is not stable for all machining

applications and cutting conditions, and there was not

seen a comparison between cryogenic treatment and other

cryogenic cooling approaches.

4. Miscellaneous effects of the cryogenic cooling in

machining processes

4.1. The effect of cryogenic temperature on material

properties

The mechanical properties of several grades of carbide

cobalt alloys (K3109, K313, K420, K68 and SP274) at

cryogenic temperatures were investigated and their inden-

tation tests indicated an increase in the hardness of all the

tested materials compared to the materials hardness at

room temperature [28,72]. These carbide grades generally

ARTICLE IN PRESS

Fig. 12. Schematic diagram of LN2 nozzle system[53].

Fig. 11. A sample of cryogenic spraying method.



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retained their toughness, high transverse rupture and

impact strength as the temperature decreased toward liquid

nitrogen temperature. So, it was determined that these

carbide tool materials were suitable for cryogenic cooling

strategies. In addition, there was not seen difference

between hardness of the cryogenically treated and un-

treated of high-speed steel (HSS) tools [70]. However,another deep cryogenic treatment test showed an increase

in hardness and toughness at AISI M2 high-speed steel

[73]. This opposition between two studies could be the

difference between the cryogenic treatment methods.

The effects of cryogenic temperature on some of work-

piece materials such as AISI 304 stainless steel [60], AISI

1008 [46,50] and 1010 low carbon steels, AISI 1070 high

carbon steel, AISI E52100 bearing steel, Ti6Al4V

titanium alloy [74] and A390 cast aluminium alloy were

also investigated. Table 1 shows cryogenic characteristics

of these materials.

Authors[28,46,50,75] evaluated some variations in tests

by observing the influence of cryogenic temperature on

chip formation. For example, the embrittlement tempera-

ture of low carbon steels was determined to be between

50 and 120 1C from standard material tensile and

impact tests. Thus, pre-cooling the workpiece or chip

cooling method was recommended for AISI 1008 and 1010

low carbon steels because of favourable chip breakability

in cryogenic machining particularly at low speeds, lower

than 6 m/s. Due to the fact that AISI 1070 and E52100

steels have high strength levels at room temperature and

their rapid and more increases in strength with decreasing

temperatures will lead to decreasing ductility and higher

cutting resistances hence, cutting zone cooling near to thetoolchip interface instead of freezing the workpiece was

recommended in cryogenic machining. Hong and Broomer

also recommended this approach for machining of AISI

304 stainless steel [60]. For cast aluminium alloy A390,

the authors recommended cooling the cutting tool instead

of workpiece. Since, keeping the cutting tool cool may

decrease the tools tendencies to adhere to the soft

aluminium matrix phase and this may reduce build-up

edge formation. Cooling the cutting tool also may enhance

its hardness and resistance to the abrasive wear of the Si

phase in A390. Ti6Al4V alloys showed rapid increase in

their strength and hardness while their toughness and

ductility showed little variation as temperature decreases.

Therefore, simultaneously cooling the workpiece to en-

hance the chemical stability of the workpiece and cooling

the cutting tool to enhance the hardness and chemical

stability of the tool were recommended as an effective

cryogenic strategy for titanium alloy [28].

4.2. The effect of cryogenic cooling on cutting temperatures

In all cryogenic cooling studies, cutting temperatures

were experimentally measured using thermocouple method

and sometimes cutting temperatures were estimated theo-

retically with finite element analysis (FEA) method by

authors to verify measurements and due to possibility of

some scatters in temperature measurement when LN2 was

employed. For instance, in cryogenic pre-cooling the

workpiece and in cryogenic tool back cooling method,

the maximum cutting temperature was estimated less than

62% and 27%, respectively, when compared with dry

cutting. In addition, reduction in maximum temperature

was estimated as 26% in cryogenic chip cooling of AISI

1008 low carbon steel [50]. These results indicated that

cryogenic pre-cooling the workpiece provided striking

results than the chip cooling in preventing cutting

temperature as determined in another study[46].

In machining of different kind of steels [6163,76], LN2

jet application reduced average cutting temperature by

about 1035% depending on the work materials, tool

geometry and cutting parameters. These measured chip

tool interface temperatures were also validated by the

predicted temperatures by FE model with an averagedeviation of 5.4%. But it was seen that cryogenic cooling

effect slightly decreased with the increase in cutting speed

and feed rate. Because, chip could be plastic or bulk at the

tool rake surface with the increase in cutting speed and this

condition could be obstruct the cryogen in penetrating the

hot toolchip interface.

Hong and Ding [53,77] compared various cryogenic

cooling strategies in machining of Ti6Al4V as shown in

Fig. 13. They found that simultaneous cryogenic rake and

flank jet cooling of the tool were four times better than the

dry cutting in terms of preventing cutting temperatures.

ARTICLE IN PRESS

Table 1

Cryogenic characteristics of some materials

Material Hardness Tensile and yield

strength

Impact strength Toughness Elongation Reduction in area

AISI 1008 m m k k k k



AISI E52100 m m k k k k

AISI 304 m 2 m

A390 m

Ti6Al4V m m 2 k

m: Increase, k: decrease, 2: no changing.



9/18

They also made a sample alignment worst to best as

regarding controlling of cutting temperature: dry cutting,

cryogenic tool back cooling (conductive remote cooling),

emulsion cooling, pre-cooling the workpiece, cryogenic

flank cooling, cryogenic rake cooling, and simultaneous

rake and flank cooling. Similar ratio between dry machin-

ing and cryogenic indirect cooling atFig. 13was obtainedin machining of RBSN with CBN 50 in another study[55].

In that study, FEA proved that the maximum temperature

on the tool fell from 1153 1C in dry cutting to 829 1C in

indirect cryogenic cooling. This reduction in temperatures

was attributed to the high conductivity of the CBN

tool. However, while the measured temperatures were

ranging between 150 and 200 1C with cryogenic indirect

cooling, they were ranging between 0 and 150 1C without

cooling[56].

4.3. The effect of cryogenic cooling on tool wear and tool life

Most of the studies examined the flank wear formation

since in practice, the amount of flank wear is used more

frequently in determining the tool life[78]. In machining of

some materials, it was obtained reductions in tool flank

wears up to five folds as seen in Table 2 with cryogenic

indirect cooling [55,56]. Similarly, in machining of AISI

304 stainless steel by indirect cryogenic cooling, tool life

was increased more than four times [79]. Another study

similarly showed that the Al2O3 ceramic inserts cooled by

indirect cooling method significantly outperformed con-

ventional dry PCBN operations [80]. Wang et al. [81]

distinctly employed a hybrid machining method in theirindirect cryogenic system with plasma heating enhanced

machining of Inconel 718 and their results indicated an

improvement of 156% in tool life when compared with

conventional machining.

If a comparison is made between cryogenic cooling

approaches, a study indicated that cryogenic tool indirect

cooling had got about 13 times wear resistance than

cryogenic chip cooling [51]. This difference between

cryogenic indirect and chip cooling was explained with

hardening of material in the case of cryogenic chip cooling

by nitrogen outflow. However, it was acquired that an

average of 30 times increase on tool life in cryogenic chip

cooling compared to the tool life for dry cutting. When

applied to machining of titanium alloy, it was expressed

that cryogenic pre-cooling the workpiece was capable of

improving tool life too[53]. In addition, Bhattacharyya et

al. [48] compared flank wear growths between two

cryogenic workpiece cooling methods, dipping the work-

piece into liquid nitrogen and continual application of

liquid nitrogen onto the testpiece in turning of Kevlar

reinforced plastics (KFRP). They obtained similar tenden-

cies but wear rate was higher with low cutting speed and

with chipbreaker tool in continual pouring of liquid

nitrogen. A comparison of machining approaches among

dry cutting, cryogenic workpiece pre-cooling and cryogenicchip cooling was done as seen in Fig. 14; both methods of

cryogenic machining performed better than dry cutting,

but cooling the chip produced the best tool life among all

[46]. It can thus be concluded from the results described

above that the indirect cryogenic cooling could exhibit

better performance than the cryogenic pre-cooling the

workpiece and chip cooling methods in tool life.

Zurecki et al. [57] made a tool life comparison between

cryogenic nitrogen cooled Al2O3-based cutting tools and

conventionally cooled CBN tools in machining of hardened

steel. They applied cryogenic coolant by spraying with a

nozzle to the rake surface of the tool. They found that

ARTICLE IN PRESS

Fig. 13. Measured and predicted tool temperatures by Hong and

Ding[53].

Table 2

Tool wears in machining of different materials

Material Cutting tool Cutting condition Cutting length (mm) Tool wear, VB(mm)

RBSN CBN50 Dry 30 2

Cryogenic 80 0.88

Ti6Al4V H13A cemented carbide Oil cooling 46 1.1

Cryogenic 46 0.22

Inconel 718 Dry 62 0.85

Cryogenic 110 0.6

Tantalum Dry 52 0.45

Cryogenic 158 0.28



10/18

cryogenic cooled Al2O3-based cutting tools endured longer

than the conventionally cooled CBN tools. They also

gained striking tool life in cutting titanium alloy as

compared to conventional flood emulsion cooling [82].

Kumar and Choudhury [58] investigated dry cutting

conditions and cryogenic LN2 spraying by a nozzle in

machining of stainless steel 202 with a carbide insert interms of tool wear. They observed about 37.39% advan-

tage in the flank wear with cryogenic machining over the

dry cutting. However, it was also observed in another study

[60] that general flooding of the LN2 to the highest

temperature area in machining AISI 304 stainless steel

caused cracking of the tool during testing at all cutting

speeds and this result was attributed to making of LN2 and

the workpiece material tougher.

A sample role of cryogenic jet cooling on tool wear was

given inFig. 15[83,84]. For instance, according to specific

value of average flank wear (VB), 0.3 mm, for SNMG

insert, the tool life increased from around 28 min under

dry/wet environment to around 70 min due to cryogenic

cooling. This means that an increase of 150% in tool life

was achieved. The authors attributed reducing in growth of

flank wear by LN2 to retention of hardness and sharpness

of the cutting edge in steady and intensive cooling,

protection from oxidation, corrosion, adhesion and ab-

sence of BUE formation. Remarkably reducing of flank

wear by SNMM insert was attributed to its geometric

structure having deep grooves parallel to the cutting edges

helping entry of larger fraction of the liquid nitrogen jets at

the flank surfaces[62,63,76].

In another cryogenic jet cooling application, best toollife result was obtained in using only Znozzle on the rake

face. For instance, tool life improvement was 67% at speed

of 3.82 m/s and 43% at the 3.40 m/s by this approach when

compared with conventional emulsion cooling. But it was

also seen at low-cutting speeds that emulsion cooling

worked slightly better than any cryogenic method [60].

In simultaneously using of two micro-nozzles that spray

LN2 to the tool rake and tool flank, tool life was up to five

times longer than in conventional machining as shown in

Fig. 16[52].

In a cryogenic cooling design [59], the effect of nozzle/

chipbreaker positioning as seen in Fig. 17 on tool life

was also studied. Among tested, six positions for

length of l and angle of l (1.75 mm151, 1.5 mm151,

1.25 mm151, 1.25 mm201, 1.25 mm101, 1 mm101)

high rate of flank wear was obtained with Position No. 1

(1.75 mm151) and No. 2 (1.5mm151). These results

were attributed to being chipbreaker far from the cutting

edge, failing in lifting up the flowing chip and hindering of

the reach of LN2. Consequently, it was found that Position

No. 3 (1.25 mm151) showed the lowest rate of flank wear.

Crater formation was also investigated with a cryogenic

jet cooling in machining of titanium alloy and the

percentage reductions in amount of maximum crater wear

with machining of 5 min were seen 33% for 70 m/min, 20%for 85 m/min and 77% for 100 m/min by cryogenic cooling

as compared to dry machining [64].

In spite of advantages of the cryogenic jet cooling

method cited in plenty of studies above, one of the studies

[85]showed that when a TiB2-coated carbide was employed

under cryogenic cooling in turning of titanium alloy

(Ti5Al5Mo2SnV), severe abrasion, adhesion and

diffusion were found on cutting tool.

In cryogenic treatment method, Yong et al. [69]analysed

the differences in tool performance between cryogeni-

cally treated and untreated inserts depending on different

ARTICLE IN PRESS

Fig. 14. Tool wears of different cooling approaches [46].

Fig. 15. (a) Average flank wear,VB and (b) average auxiliary flank wear, VS, for 30 min [83].



11/18

cutting periods and breaks in turning of ASSAB 760

medium carbon steel. They obtained reductions in flank

wear between 4% and 20% and increases in tool life

between 1.05 and 1.3 times. They [86] also investigated

cryogenically treated tungsten carbide tool performance

during the high-speed face milling of the same material.

Cryogenically treated inserts performed an increase of up

to 38.6% in tool life over the untreated inserts in dry and

wet cutting conditions in their results. When HSS tools

were cryogenically treated, it was noticed that increasing

both the speed and feed reduced tool lives regardless the

heat treatment submitted by the tool. Cryogenically treated

tools presented longer tool lives with increases up to 44%

in the brandsma rapid facing test. Performance of the

treated tools gained from 65% to 343% depending on the

cutting conditions during drilling steels. However, cryo-

genically treated coated HSS milling cutters presented

worse performance than untreated tools [70]. In another

study, cryogenically treated HSS drills were used in drilling

stainless steel work materials. Results of the study

indicated significant improvements in tool life of treated

drills[87]. Kim and Ramulu[88]used cryogenically treated

carbide tools in drilling thermoplastic composites to

investigate machinability in terms of the drilled hole

quality and tool wear. Their findings showed that while

the cryogenically treated carbide tools produced better hole

qualities than the conventional carbide tools, conventional

carbide tools showed better wear resistance than the

cryogenic treated carbide tools. In a different application,

tool wear was reduced when cryogenically treated tungsten

carbide tools were used in turning of fibreboards [89].

4.4. The effect of cryogenic cooling on surface roughness

and dimensional deviation

Surface roughness is generated from two components,

the ideal or geometric finish and natural finish. While the

ideal or geometric finish results from the geometry and

kinematic motions of the tool, the natural finish can result

from vibrations, tool wear or built-up edge formation, etc.

[90]. The dimensional deviation or inaccuracy is deter-

mined as the difference between applied depth of cut and

obtained depth of cut [91], and the finished job diameter

generally deviates from its desired value with the progress

of machining. Accuracy is highly affected by the cutting

forces and the stiffness of the cutting tool, the tool holder

and part fixtures [92]. Surface finish and dimensional

deviation could be also affected even with very stiff and

accurate machine tools. In such a condition, negativity was

correlated with high-cutting temperature and insufficient

cooling[93].

One example of cryogenic jet cooling on dimensional

deviation and surface roughness was shown in Fig. 18.

Values of dimensional deviation and surface roughness

obtained less than dry and wet machining under cryogenic

cooling. Moreover, conventionally applied cutting fluiddeteriorated the surface roughness compared to dry

machining. Surface roughness increased with the increase

in feed rate and decreased with increase in cutting speed

under all environments (dry, wet, cry). Authors attributed

reduction in surface roughness and dimensional deviation

in cryogenic machining to reduction in auxiliary flank wear

because of keeping of tool hardness[62,63,76,83,84].

In application of indirect cryogenic cooling, the surface

roughnesses of materials machined with LN2 cooling were

found to be much better than the surface roughness of

materials machined without LN2 cooling after the same

length of cutting as seen in Table 3. The large differences

were attributed to the variation in the tool wear. Since, the

tool wear increased with the length of cut and the surface

roughness increased with tool wear [56]. In hybrid

machining method of Wang et al. [81], cryogenic indirect

cooling system with plasma heating, provided a 250%

improvement in surface roughness in machining of Inconel

718 when compared with conventional machining.

In the study of Bhattacharyya et al. [48], better surface

finish was obtained with continual flooding of liquid

nitrogen onto workpiece, compared with freezing method.

However, a comparison between dry machining, cryogenic

chip cooling and indirect cryogenic cooling were made as

seen inFig. 19. The best results were obtained with indirect

ARTICLE IN PRESS

Fig. 16. Tool life comparison for cryogenic jet cooling and emulsion

cooling curve on loglog scale [52].

Fig. 17. Chipbreaker/nozzle positioning [65].



12/18

cooling (cryo 2) and the worst results with chip cooling

(cryo 1). This case was explained with cryogenic cooling of

the workpiece in the case of cryo 1 resulted in a harder

workpiece than the other cases.

4.5. The effect of cryogenic cooling on friction

It was stated that nitrogen must have some sort of

positive boundary lubrication effect. Strong adhesion

between the tool rake and chip face occurs in dry cutting

conditions and lower temperatures could make the material

harder and less sticky by reducing adhesion between

interacting surfaces and thus resulting in a low friction

[4,65,94].

Hong et al. [95] presented an experimental sliding

contact test setup on CNC turning centre composed of a

carbide tool and Ti6Al4V titanium alloy and AISI 1018

low carbon steel disks. Their findings showed that the LN2

lubricated contact produced lower friction coefficient

than the dry sliding contact and the emulsion-lubricated

contact for both disk materials. After, Hong [94] investi-

gated lubrication mechanisms of LN2 in detail with five

tribological disk-flat tests as shown inFig. 20. He adapted

two possible LN2 lubrication mechanisms to the test

setup, the temperature effect forming a physical barrier by

ARTICLE IN PRESS

Fig. 18. (a) Surface roughness and (b) variation in change in dimension [63].

Table 3

Surface roughness values

Material Cutting condition Cutting tool Cutting length (mm) Surface roughness, Ra (mm)

RBSN LN2 CBN50 160 3.2

Dry 30 20

LN2 VC734 30 7.8

Dry 6 25

LN2 VC722 70 6.7

Dry 8 22

Ti6Al4V LN2 H13A cemented carbide 108 1.9

Dry 40 15

Inconel 718 LN2 65 1.5

Dry 7.8

Tantalum LN2 25 0.9

Dry 3.8

Fig. 19. Comparison of surface finish[51].



13/18

cooling the disk, the flat or both, and the hydrodynamic

effect injecting LN2 to the between two contact samples.

To study the LN2 lubrication effect on materials, five pairs

of materials were used to conduct the friction test: AISI

1018 disk vs. AISI 1018 specimen, AISI 1018 disk vs.

uncoated insert, AISI 1018 disk vs. coated carbide insert,

Ti6Al4V disk vs. uncoated carbide insert, andTi6Al4V vs. coated carbide insert. In all cases, jet

cooling between the disk and the tool insert achieved the

best friction reduction regardless of material pair by

generating hydrodynamic films (c), also the uncoated

carbide insert responded better to cryogenic cooling in

reduction of friction while coating was effective in reducing

friction under dry conditions. This result was attributed to

the reduction of friction force by changes of tool material

properties. When regarding temperature effect, it was also

stated that the testing results indicated that the low

temperature properties of tool insert material were more

critical than the workpiece material in determining the LN2

lubrication effect.

For cryogenic jet cooling method, it was claimed when

LN2 was sprayed to the tool tip, it formed a fluid/gas

cushion between the chip and tool face and provided

lubrication effect by absorbing the heat and evaporating

quickly[15]. Metallurgical evidence of friction reduction in

cryogenic machining was also proved and the reduction in

secondary deformation zone layer (SDZ) thickness by the

cryogenic jet cooling was substantiated as reducing friction

between the tool rake and the chip[65]. This reduction was

attributed to a combination of the cooling effect, which

changes the mechanical properties of the tool surface

asperities favourably and the lubrication effect of a highpressure LN2 cushion at the toolchip interface, considered

by the chip lift-up action of the integrated nozzle/chip-

breaker. The effect of chipbreaker position, as seen in

Fig. 17, on friction between the chip and the tool also

examined in cryogenic jet cooling and the lowest friction

coefficient on the toolchip interface was observed with

Position No. 3 (1.25mm151) as seen in Fig. 21. In

addition, an arrangement was made between dry cutting

and cryogenic jet cooling methods according to friction

coefficient as dry cutting4cryogenic flank cooling4cryo-genic rake cooling4both rake and flank cooling.

4.6. The effect of cryogenic cooling on cutting forces

Energy consumption in a cutting operation was asso-

ciated with friction and cutting forces [5]. So, it is

significant being cutting forces less in terms of productivity

and production cost in any machining process. Bhatta-

charyya et al.[48] cooled the Kevlar composite workpieces

by cryogenic freezing and continual flooding methods

during machining. They measured the cutting forces and

they found that the cutting forces were about 50% higher

with cryogenic freezing of the workpiece, compared with

those obtained in flooding. In addition, cutting forces

recorded with chipbreaker tool were lower than those with

a non-chipbreaker tool. On the other hand, shearing force

Fswas calculated for comparison of cryogenic chip cooling

and workpiece pre-cooling from the measured force

componentsFc,Ftand Ffas seen inFig. 22. Both cryogenic

chip cooling and cryogenic workpiece pre-cooling pro-

duced an increased shear force compared to dry cutting,

but by different margins. For instance, at a cutting speed of

6 m/s, the shear force increased less than 8% in chip

cooling, while with workpiece pre-cooling the increase was

more than 37%. However, pre-cooling the workpiececaused more increase in shear forces than the chip cooling.

Consequently, cutting forces will increase with any

cryogenic workpiece or chip cooling approaches.

ARTICLE IN PRESS

Fig. 20. Five cases of LN2 application: (a) specimen under LN2 cooling/bath to study the effect of cryogenic temperatures on the tool material; (b) sample

disk under LN2 cooling/in LN2 saturated enclosure to study the effect of cryogenic temperatures on the workpiece material; (c) LN2 jetting between

specimen and sample disk to study hydrodynamic effects on the contact and local cooling; (d) jetting and cooling a specimen to study the combined effect

of the hydrodynamic film and the low temperature tool; (e) specimen and sample disk under LN2 cooling without LN2 at contact for comparison with the

results from (a) and (b). A dry run friction test was also conducted for comparison [94].



14/18

Wang and Rajurkar [56] measured the cutting forces in

using of their indirect cryogenic cooling system. They

showed that cryogenic cooling did not significantly alter

the cutting forces in machining of different materials

(RBSN, Ti6Al4V, Inconel 718, and Tantalum) and the

reason was explained with restricting of the cryogenic to

the cutting insert not to the workpiece. Remarkable force

difference in turning titanium and Inconel was explained

by chip entanglement and the leaking of the liquid due to

inappropriate installation of the reservoir cap. However,Wang et al. [81]achieved reducing cutting forces approxi-

mately 3050% in machining of Inconel 718 with a hybrid

machining method, cryogenic indirect cooling system with

plasma heating developed by them.

In cryogenic jet cooling condition, the cutting forces

comparison was given in Fig. 23. Findings showed that

all cryogenic machining approaches (rake, flank, rake

and flank) had higher main cutting force and thrust

force. According to the authors, lower cutting tempera-

tures caused stronger and harder workpiece material.

This case resulted in increasing cutting forces. It was also

proved that feed force, which is closely related to the

frictional force of the chip acting on the tool, decreased

because of lower friction in cold temperatures. But,

the lowest feed force was obtained only in rake cooling.

It was also seen that the friction force reduction in the

direction of chip flow was more than the cutting force

increase. However, in contrast to the above cited, Dhar

et al. [96] results indicated the possibility of a substantial

reduction in cutting forces by favourable chip formation

in turning of AISI 1040 and AISI 4320 steels with

cryogenic cooling by liquid nitrogen jets. Similarly,

Kumar and Choudhury [58] observed about 14.83%

advantage over dry cutting with cryogenic LN2 spraying

by a nozzle in machining of stainless steel 202.These oppositions could be attributed the workpiece

materials, used in tests, and their properties in cryogenic

temperatures.

ARTICLE IN PRESS

Fig. 21. Friction coefficients at different chipbreaker positions [65].

Fig. 22. Shear forces for different cooling conditions[46].

Fig. 23. Cutting forces in different cooling condition at 1.5 m/s[65].



15/18

5. Conclusions

The aim of this study is to analyse and point out the

effect of cryogenic liquid nitrogen cooling on cutting

performance in material removal operations and its

application methods. Other conventional coolants, heat

generation and temperature distribution in a cuttingprocess have been also discussed. Following consequences

can be drawn from this review.

Cryogenic cooling in metal cutting has been studied

nearly for six decades, however, many of the studies

and most remarkable of them particularly in terms of

application methods have been done in last decade

and striking results have been achieved. Cryogenic cooling

is still attractive and has been examined in material

cutting field.

Almost all type of materials from ductile to hard and

brittles have been machined in cryogenic cooling studies by

many miscellaneous cutting tools. However, different kinds

of steels were used widely in tests; non-ferrous metals, non-

metallic and composite materials should be examined

more. In addition, most of the studies have included

turning operations. Other machining operations such

as milling and drilling could be attempted more with

cryogenic cooling.

When compared with dry cutting and conventional

cooling, the most considerable characteristics of the

cryogenic cooling application in machining operations

could be determined as enabling substantial improvement

in tool life and surface finish-dimensional accuracy through

reduction in tool wear through control of machining

temperature desirably at the cutting zone.

Cryogenic cooling has been executed in cutting opera-

tions in different ways by using liquid nitrogen for pre-cooling the workpiece, cooling the chip, cooling the cutting

tool and cutting zone. Cutting tool and cutting zone have

been cooled cryogenically by heat transmission, general

repulsing of the coolant to the cutting zone and spraying in

jets with nozzles too. Cold temperatures were also used for

strengthening of the cutting tools by cryogenic treatment.

Many studies have been done to explore the most efficient

one. In these studies, comparisons have been made between

conventional cutting strategies and cryogenic cooling

methods, however, opposite outcomes have been proved

by the researchers such as producing of the LN2 jet

application was the best results [53,65], providing of

indirect cryogenic cooling better performance than LN2

sprays [51,55,56] and being cooling of the tool more

significant than the cooling of workpiece at high-cutting

speeds in cryogenic machining and the opposite claim at

low-cutting speeds regarding of tool life. Consequently, the

conclusions described above could change relating to

toolworkpice pairs and cutting conditions. A general

evaluation of this review was given in Table 4.

ARTICLE IN PRESS

Table 4

The evaluation of the cryogenic cooling studies

Cryogenic cooling

method

Workpiece material Cutting tool Machining

method

Inv esti gatio n t opi cs Au thor s

Cryogenic workpiece

and chip cooling

Kevlar reinforced

plastics (KFRP)

Uncoated carbide

(TPUX

160304TPUN

160304)

Tu rnin g Too l flan k we ar, c uttin g

forces, surface finish

Bhattacharyya el al. [48]

AISI 1008 Carbide

(CNMA432KC850)

Turning Material properties, chip

breakability, cutting

temperature

Hong et al. [50]

Hong and Ding [46]

AISI 4340 Carbide (SNMG

120408-26)

Tu rnin g Too l we ar/li fe su rfac e

roughness

Ahmed et al. [51]

Indirect cryogenic

cooling

Stainless steel Diamond tools Turning Tool wear, surface finish Evans[44]

Ceramic (RBSN-

reaction bondedsilicon nitride)

PCBN50

(polycrystalline cubicboron nitride)

Tu rnin g Too l flan k we ar, c uttin g

forces, cuttingtemperatures, surface finish,

stress analysis

Wang and Rajurkar

[54,56]

Ti6Al4V Cemented carbide Wang et al. [81]

Inconel 718 WG 300 ceramic

Tantalum


120408-26)

Tu rnin g Too l we ar/li fe su rfac e

roughness

Ahmed et al. [51]

AISI 304 stainless

steel

TiCN-coated carbide Khan and Ahmed[79]

Cryogenic spraying 52100 bearing steel Al2O3 ceramic

(alumina ceramic)

Turning Surface roughness, tool life Zurecki et al. [45,57,82]

A2 tool steel PCBN

(polycrystalline cubic

boron nitride)



16/18

Acknowledgement

The authors wish to express their gratitude for financial

support of the cryogenic machining project by The

Scientific and Technological Research Council of Turkey

(TUBITAK), Project no. 106M473.

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ARTICLE IN PRESS

Table 4 (continued)

Cryogenic cooling

method

Workpiece material Cutting tool Machining

method

Inve stig atio n to pic s Auth ors

WC-Co PCD (polycrystalline

diamond)

Titanium alloy

Stainless steel 202 Carbide (TPUN

160304)

Tur ning Cutti ng for ce, too l flan k

wear

Kumar and Choudhury

[58]

Cryogenic jet cooling AISI 1060 Carbide (SNMG

120408-26, SNMM

120408-26)

Tur ning Tool flank w ear , sur face

roughness, dimensional

deviation, cutting

temperature, chip

formation, cutting forces

Paul et al. [83,84]

AISI 1040 Dhar et al. [61,62,76,96]

E4340C

AISI 4140

AISI 4320


120408-26)

Turning Dhar and

Kamruzzaman [63]

AISI 304 stainless

steel

Carbide (CNMG

432)

Turning Material properties, tool

flank-crater wear,

production cost-

productivity, friction,cutting forces

Hong and Broomer[60]

Ti6Al4V Uncoated carbide

(CNMA 432-K68)

Turning Hong et al. [65]

AISI 1018 Turning Hong et al. [52]

Ti6Al4V Microcrystalline

uncoated carbide

(SNMA 120408)

Tur ning Tool flank -cr ater we ar,

cutting forces, surface

roughness

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Ti5Al5Mo2SnV TiB2-coated carbide

AISI 1018 and 4140 M7 HSS Milling Tool flank wear, tool life Hong et al. [24,25]

Ti 6-4

Al 6160

A390

PVC

Cryogenic treatment Stainless steel HSS Drilling Tool life Chatterjee[87]ASSAB 760 medium

carbon steel

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230408)

Turning Tool flank wear, tool life Yong et al. [69,86]

Milling

HSS Drilling,

Milling

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hardness

Silva et al. [70]

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composites

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Fiberboard Carbide Turning Tool wear Stewart[89]



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