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completion of its formation process. characterizedby the strength of interparticle contacts which isestablished by comparison of kinetic dependencesof BN-BN transformation under hot compaction ofBN and results of measurement ofsintered materialhardness. made by the method of microhardness,

Coatings

DEVELOPMENT OF COATED CARBIDE CUTTINGTOOL INSERTS FOR MILLING OF CAST IRON

E Matsumoto. et aI. (Sumitomo Electric IndustriesLtd. Tokyo. Japan), Int, J, Refractory Metals & HardMaterials. Vol 9. No 1. 1990. 25-31.

Cemented carbide inserts have been in usc for sometime now for the rough milling ofcast iron, In recentycars. however. there has been much call for thereduction of machining costs. and hence anincreased demand for high-efficiency machining,Although tool materials ha\'e been graduallychanging from the cemented carbide of the past tocoated carbide. the ratio of coated carbides is stillvery low when compared with the field of turning.

WEAR RESISTANCE OF MoSZ CONTAININGCOATINGS

V K Kadyrov. et aI. Poroskomya Metallurgiya. No.1. 1989. 25-28. In Russian.

Detonational composite coatings produced fromalloyed nichrome. where dispersed molybdenumdisulphide is used as structural component arctested for wear resistance. Their high serviceabilityand prospects of use for friction nodes wearprotection are noted.

BASICS OF PHYSICAL VAPOUR DEPOSITIONPROCESSES

H Heinrich. et al. (RW-TUV, Essen, Germany).Metall., Vol. 44. No 3. 1990. 279-283. In German.

Areport is given on the basics of the PVD (PhysicalVapour Deposition) process and its three variantsvacuum evaporation. spullering and ion-plating.The mechanisms of the formation and growth of thelayers are described with the hdp of interface zonesand Thornton's structure-zone model. Theinfluence of some process parameters is shown.Emphasis is laid on the ion-plating process becauseit combines the advantages of both the othervariants.

Electric/Magnetic Materials

BEIlAVIOUR OF W·Cu CONTACTS IN AIR ANDOIL

RVMinakova. et al. Poroskomya Metallurgiya, No.1,1989,51- 57. In Russian.

Equilibrium reactions in the W-Cu-C-O-H systemand their correlation with peculiarities of wear of\V-Cu contacts under the influence of high-currentarc are analysed. It is stated that the surface stateafter the mechanical processing and tungsten

MPR June 1990

oxides e\'aporalion affect electric erosion ofcontacts at first cycles of disconnection and smallcurrent. A set of chemical reactions and processeswhich cause erosion of contacts under repeatedcommutation of intense current in the air and in theoil is influenced by enrichment ofcontacts workinglayer by tungsten, oxidation and carburisation.imprm'ing the role ofbrillIe failure ofworking layer,which occurs under effect of discharge togetherwith evaporation and spraying of components.

1I0T FORGING OF Ba-Sr·Ca·Cu·OSUPERCONDUCTOR POWDER

T Nishida. et aI. J. Japan Soc. POIl'der and POll'derMetallurgy, Vol. 37, No. I, 1990. 77-82. In Japanese.

Bi2Sr2CaCu20, ceramic powder prepared bysolid-state reaction was encapsulated in a stainlesssteel mould. The mould was heated at 840C for 10minutes and press-forged rapidly under variousuniaxial compressive loads to avoid excessi\'e heatloss. Density of the processed ceramics wasestimated from the results of Vickers hardness (Hv)measurement. The orientation of thesuperconducting (001) plane of the crystal grainswas determined by X-ray diffraction analysis of thepolished surface of the ceramics. The values of H\'and f increased with an increase in the deformationratio of the mould during the processing.

IIIP TREATMENT OF Bi·Pb OXIDESUPERCONDUCTOR

J Takada. et a!. J. Japan Soc. POll'der and POIl'derMetallurgy. Vol. 37, No.1. 1990.83-88. In Japanese.

Influences of HIP treatment on the densification ofthe Bi-Pb oxide high-Tc ceramics and the electricalconducti\·ity have been studied on the sample withnominal composition of Bio,9l\Pbo,2,Sr\OCal.lCUI.60,. The density allained was over 90% oftheoretical density ofthe Bi-Pb high-Tc phase by theHIP treatment at 850C for 2h. The electricalresistance of the sample without HIP treatmentdecreased with decreasing temperature from 280Kto 120K and dropped to zero ncar lOOK, That of theHIP treated sample increased semiconductivelybetween the temperature range from 280K to 110K.and below 110K gradually dropped to zero at50-70K.

IIIGH Te Bi-Pb-Sr-Ca-Cu-O SUPERCONDUCTORPREPARED BY PLASTICISED EXTRUSION

YNishikawa. et aI. J. Japan Soc. POIl'der and POll'derMetallurgy, Vol. 37, No I, 1990. 89-93, In Japanese.

Plasticized superconducting raw compounds wereextruded as wire and strip Bi. Pb-Sr-Ca-Cu oxideshave been produced by solid-state reactions. TheywefC calcined at 850C for 50 hours. ground. fC­calcined and re-ground. The composition ofSuper-conducting powders were Bio,1Pbo,lSrCaCu\.50y_

PREPARATION OF SUPERCONDUCTING OXIDEIN ATIRITION MILL

M Naito. et aI. J. Japan Soc. POII'der and POII'derMetallurgy, Vol. 37, No. 1. 1990. 131-133. InJapanese.

Adry allrition type mill was modified and can grinddifferent kinds of powder materials down tosubmicron le\·el. disperse them uniforml\' andchange them into composite particles. In this-paper,this apparatus was applied to prepare the rawmaterials ofY-Ba-Cu-O superconductors. Althoughthese raw materials were treated in single calciningand grinding processes. the obtainedsuperconductors showed the critical temperature of90K class and the diffraction pallern oforthorhombic crystal structure of Y- Ba-Cu-O.

First International High SpeedSteel Conference

The abstracts below are a furtherselection from the papers presented atthe above conference which was heldin Leaben, Austria, March 26-28,1990.

INVESTIGATION OF MICROSTRUCTURE ANDMECHANICAL PROPERTIES OF AN ADVANCEDT15 HSS

B Hribernik. et al. (Bohler GmbH. Kapfenberg.Austria]

The production of high speed steels by PM leads. incomparison to conventionally produced high sfeedsteels. to significantly finer microstructure withhomogeneously distributed carbides. This paperpfCsents results of investigations on microstructureand mechanical properties of TI5 modified HSS.The mechanical properties were determined in theoptimal heat treated condition. The compressiveyield strength of the investigated material iscomparable to cemented carbides with a highCo-content. On the other hand toughness is alsosatisfactory. The optimal heat treated materialshows higher bend rupture strengths than otherwell known PM-high speed steels. First yield testsha\'e shown that the material offers imprm'ed wearresistance than comparable PM-HSS,

WEAR TESTING OF SINTERED I1IGII SPEEDSTEELS

D S Coleman. P R Brewin. (Inst. of Pol\'merTechnology and ~Iaterials Engineering.Loughborough University of Technology, UK).

This paper describes a 'crossed cylinder' abrash'ewear test used-at Loughborough to test PM HSS. Thefactors and the parameters involved in this abrasivewear test have becn extensivelY examined in closecollaboration with an alloy ste~l powder producer.Usc is made of the wear hypothesis described by JF Archard. which relates the wear beha\'iour of amaterial to the abrash'e conditions, the loadsapplied to it during service, the sliding distancetravelled and the time ofservice. Results of \\'ear teston specimens. with high alloy compositions madeby PM methods. wcre presented and compared withresults of specimens with similar compositionsmade by the conventional means ofcasting. forgingand other methods, such as hot isostatic pressing.The relationship with composition, heat treatmentand the effect these ha\'e on the microstructure arc

487

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discussed. in conjunction with the resultant wearbehaviour of these materials.

CHARACTERIZATION OF CARBIDES IN PMIIIGH SPEED STEELS

G Principi. et al, (Dept. of Mechanical Engineering.Unh'Crsity of Padua. Italy)

High speed steels produced by a powder methodhave been submitted to quenching and temperingto obtain the proper service structure. Themorphology of the \'ery finely dispersed carbidespresent in the specimens in the different steps oftreatment has been observed by SEM. X·raydiffraction and Miissbauer spectroscopy in CXMSconfiguration have been used to evaluate carbidesand retained austenite after the various temperingstages. Chemically and electrolytically extractedcarbides have been analysed by X-ray diffractionand Miissbauer .spectroscopy in transmissiongeometry. It is found that the carbides arc mainly of

. the Moe and MC type.

WEAR MECHANISMS AND STRESS STATE INPM IIIGII SPEED STEELS DURING MILLING

HChandrasekaran. el al (Swedish Institute for MetalResearch, Stockholm. Sweden).

This paper discusses the results of basic studies onsingle tooth peripheral milling of steel workpiecewith PM HSS inserts carried out in an attempt 10effectively understand the complexend millingprocess. The results were compared with thoseobtained from end milling tests. with specialreference. to tool·tip stress state. observed \\'earmodes and the fatigue properties of the toolmaterial.

INFLUENCE OF SUBSTRATE MATERIAL ONCUTTING PERFORMANCE OF lIARD COATEDTOOLS

E Haberling. \V Koster (Thyssen Edelstahlwerke.AG. Krefeld, Germany).

Hard coating of high speed steels by PVD is the mostimportant contribution to the impro\'ement of thecutting performance of steels since high speed toolsteels were developed. Coating the tool with a hardlayer of 1 to 5 11m thickness protects it against wearthus increasing the life time by 300 to 1000%.

DEVELOPMENTS OF P"D COATINGS FOR IIIGlISPEED STEEL

JEbberink. (G Guhring Ag. Albstadt. Germany)

Up to 19B5three physical vapour deposition (PVD)techniques were used to ion-plate HSS at lowtemperatures (c560C) with TiN: electron beame\'aporation, arc discharge and magnetronsputtering. Electron beam evaporation and the arcprocess are now used in the tool industry to coatHSS with TiN.

cmlPARISON OF FRACTURE TOUGHNESS OFIIIP, FORGED AND SINTERED TI5 IIIGH SPEEDSTEEL

M II Poech, et aJ. (Max Planck Inslitut fUrMetallforschung. Stuttgart. Germany).

488

Fracture toughness measurements were made onsamples of PM HSS of type Tl5 made by HIring.forged and sintered. Gas atomized powder was usedfor HIPed steel and water atomized for the forgedand sintered specimens. Mean carbide particle sizeswere found. by lineal measurement to be 0.24. 0.54and 1.56 11m respecti\·ely. Crack resistance of theHIPed steel was found to be one half of that of thesintered steel at equal hardness. O\'eragingincreased the fracture toughness of the sinteredsteel but no increase was found for the HIPed steel.Low toughness of the HIPed steel is explained.

WEAR BEllAVIOUR IN INTERRUPTED CUTTINGOF PM IIIGII SPEED STEELS

GZamboni. et al. (Dept. of Mechanical Engineering.Uni\'ersity of Padua, Italy)

Inserts of the high speed steels produced by a PMmethod have been compared to similar inserts oftraditional high speed steels by means of turninginterrupted cutting tests on AISI 1040 steel. In thisway milling working has also been simulated. Thegradual wear behaviour on the race and on the flankof the inserts and untimely failure (chipping.fracture and breaking) of the CUlling edges havebeen analysed. In particular the form of wear hasbeen obsef\'ed (adhesion. abrasion and diffusion)by SEM and the amount measured. The obtainedresulls evidence that the P~I steels behave betterthan the traditional high speed steels; finally theyhave been correlated to the microstructuralcharacteristics. specially regarding to the amountand the type ofcarbides present in the utilized tools.

EFFECT OF COATING THICKNESS ON CUTTINGPERFORMANCE OF CVD TiN COATED IIIGHSPEED STEELS

A B Smilh. et al, (Institule of Polymer Technologyand Materials Science. Loughborough University ofTechnology. UK)

Turning used to study effect of TiN coatings ofHSStool inserts in lests continued without stopping tofailure and in tests interrupted for inspection ofthetools. Variation in coating thickness found to besignificant in range O·BlIm. T\\'o-fold increase intool life found at 211m. little change in range 2-411mand rapid increase in life up to 711m. Above 7l1m toollife decreased rapidly.

Mechanical Alloying

MECHANOCHEMICAL ALLOYING OF Ni WITHCu

M Luthardt. et al. Neue Hutte. Vol. 35. No 2. 1990.60-66. [n German.

Intensive mechanical treatment of powder metalmixtures may resull in an homogenization at atomiclevel. i. e a fonnation of solid solutions and alloys.In proper cases. as in the given Cu - Ni system. thedeveloping mechanical stress speeds up the masstransfer extraordinarily and causes it to proceed inone direction only. This transfcrspeedofthe copperatoms into the nickel lattice exceeds diffusion speedby many orders of magnitude even when taking into

account the high dislocation density. In such casesa short-time mechanical treatment enables powdermetallurgical alloying to take place e\'en at roomtemperature.

MECHANICAL ALLOYING OF Cu WITH NbC ANDTaC

T Takahashi. Y Hashimoto (Industrial ResearchInstitute of Hyogo. Kobe. Japan. f. Japan Inst. ofMetals. Vol. 54. No.1. 1990. 67- 75. In Japanese.

To prepare a dispersion·strengthened Cu.mechanical alloying was carried out using pure Cu.Nb. Ta and graphite pO\\·ders. After the mechanicalalloying for 40 hours. the Cu·Nb-C solid solution +NbC mixture powder and the Cu-Ta-C solidsolution +Ta +TaC mixture powdci- were obtainedin the Cu·Nb-C and Cu-Ta-C system. respectively.These powders were heat·treated in a vacuum atvarious temperatures from 873 to 1323 K. In theCu-Nb-C and Cu· Ta·C systems. l':b and C or Ta andCreacted. resulting in precipitation ofvery fine NbCand TaC particles in copper.

Metal Injection Moulding

INJECTION MOULDING OF 1\10 POWDER

Y Kaneko. et al, J. Japan Sac. POll'der and Pall'derMetallurgy.' Vol. 37. No 2. 1990. 191-193. InJapanese.

Injection moulding of Mo powder using anacrylate·APP (atactic- polypropyrcne)-wax bindersystem was carried out. The moulding compositionwas 54.6% Mo powder. IB.B% acrylate. 10.9% APP.11.6% wax and 3.9% dibutyl phtalate in \·olume.The green parts \\'ere debinded in air and sinteredat 1700C for 19 hr in hydrogen. The relali\'e densityof sintered specimen was 93.0-93.5%. The carbonand oxygen content of sintered specimen were 46and 224ppm.

APPLICATION OF INJECTION MOULDING TO CuPOWDERS

H Uraoka. et al. J. Japan Sac. Pall'der and Pall'derMetallurgy. Vol. 37. No 2. 1990. 1B7-199. InJapanese.

The injection moulding ofCu powder by four kindsof binder systems (A.B.C,D) was investigated. Thebinder system (A) consisted of special-acrylatecopolymer (AC). atactic polypropylene (APP).paraffin wax (wax) and di·n·butyl phthalate (OBP);(B) consisted of ethylene·vinylacetate copolymer(EVA), polybutylmethacrylate (PB~IA). wax andDBP; (C) consisted of polyethylene (PE).special-polyvinylalcohol copolymer. wax andstearic acid (St); (D) consisted of polystyrene (PS).PBMA. APP. wax and DBr. The green body. buriedin sand. was debinded during heating from roomtemperature to 300C (B) or 320C (A.C.D) in air. Thedebinded part was sintered at 950 C (A). 970 and1020C (B.C.D) in Hz and Ar. The sintered part usedthe binder system (A) and the sintered part at 1020eused the binder systems (B,D) had a relative densitvof over 95%. The density of sintered part relates tothe debinding process. The sintered part usingbinder system (AI showed tensile strength of28.27kgflmmz• elongation of 48.5%.

MPR June 1990