Hardness Testing

METALLURGY & MATERIALS DEPARTMENT

ENGINEERING FACULTY - UNIVERSITY OF INDONESIA

DEFINITION

Hardness - "ability to resist permanent indentation"

Testing Methods :

1. Indentation hardness2. Rebound hardness3. Scratch hardness

Purpose of Hardness Test:

1. Measure the hardness value of materials2. Used to give an indication of tensile strength and the ability to resist wear

Scratch Hardness Invented by : Friedrich Mohs (German mineralogist) Method :

A qualitative Moh’s scale, determined by the ability of a material to scratch another material: from 1 (softest = talc) to 10 (hardest = diamond).

Indenter : Diamond

Diamond10

Corundum 9

Topaz 8

Quartz 7 steel file

Orthoclase (feldspar)

6

Apatite 5 Knife

Flourite 4

Calcite 3 Cupper Coin = 3

Gypsum 2

Talc 1

Scratch Hardness

Not suitable for Metals very wide scale Low Precision & No Accurate.Low Precision & No Accurate.

Conversion Conversion Diagram from Diagram from

Mohs ScaleMohs Scale

Dynamic Hardness Tests

Shore Scleroscope (ASTM E 448) - Measures the rebound of a small pointed

device dropped from a 254mm height. Schmidt Hammer - Measures rebound of

a spring loaded hammer. The test has been correlated with concrete compressive strength.

SCLEROSCOPE

INDENTATION HARDNESS

Method : Press a hardened steel ball or diamond into the material to be tested under an applied force

Indentation Hardness : Brinell Vickers Rockwell Knoop

Indentation Hardness Testing of Metals

Brinell Hardness Test (ASTM E 10) - Commonly used.

Rockwell Hardness Test (ASTM E 18) - Commonly used. Indentor and loads are smaller than with the Brinell test.

Vickers Hardness Test (ASTM E 92) - Similar to Rockwell. Uses a square-based diamond pyramid for the indentor.

Knoop (Tukon) Hardness Test - used for very thin and/or very small specimens.

Brinell Hardness A Load applied to a 10mm diameter ball. Measure diameter of the indentation to the

nearest 0.02 mm under a microscope. Compute the Brinell Hardness Number (Bhn)

– D = diameter of ball (mm) D = 10mm

– d = diameter of indentation (mm)– P = applied load (units = kg)

22

2area indented

mass Load

dDDD

PBhn

Indentation of Brinell

Brinell indentation in the surface of materialBrinell indentation in the surface of material

Important Bhn Variables Thickness of Specimen:

Proximity to edge or other test locations: – The distance of the center of the indentation from the edge or

from the center of adjacent indentations 2.5 times the diameter of the indentation.

Thickness of specimen (mm)

Minimum Brinell hardness for which

a Brinell test may safely be made

500 kg load 1,500 kg load 300 kg load

2 79 238 476

4 40 119 238

6 26 79 159

8 20 60 119

10 16 48 95

Material Brinell Hardness

Pure Aluminum 15

Pure Copper 35

Mild Steel 120

304 Stainless Steel 250

Hardened Tool Steel 650/700

Hard Chromium Plate 1000

Chromium Carbide 1200

Tungsten Carbide 1400

Titanium Carbide 2400

Diamond 8000

Sand 1000

In general, vickers method is similar to Brinell method, but their difference is the type of indenter.

Indenter : Pyramid diamond - 136o

The Indented shape : cubic, measured by optical microscope

d1 + d2 2

- d = 0,375 D

- d - d ==

Vickers Hardness Test

Vickers Hardness

vickers hardness Equipment

Vickers Indenter

Indented Shape (see by optical microscope)

Vickers Hardness (ASTM E 92)

The formula :

1,8544 P d2

P = Load (kg) 1-120 kgd = Length of diagonal (mm)

VHN VHN ==

The Effects of Vickers Hardness in

Materials

Rockwell Hardness (ASTM E 18)

Invented by S.P Rockwell in 1922

Indenter :Rockwell C using a Diamond - 120o

Rockwell B using a Hardened Steel Ball

It is easy to perform and the hardness number is obtained directly from the testing machine.

The test consists of applying a minor load of 10 kg to seat the indenter and then applying a major load (typically 100 kg) to create a permanent depression beyond that caused by the minor load.

The hardness number, which is read directly from a dial or digital scale on the testing machine, is inversely related to the additional penetration caused by application of the major load

Rockwell Hardness

Rockwell Indenter

Rockwell Hardness Scale

Scale Symbol

IndenterMajor Load,

kgfDial Figure Typical Applications

A Diamond 60 BlackCemented carbides, thin steel, and shallow case-hardened steel

B 1/16" ball 100 RedCopper alloys, soft steels, aluminum alloys, malleable iron

C Diamond 150 BlackSteel, hard cast irons, pearlitic malleable iron, titanium, deep case-hardened steel, and other materials harder than HRB 100

D Diamond 100 BlackThin steel and medium case-hardened steel and pearlitic malleable iron

E 1/8" ball 100 RedCast iron, aluminum and magnesium alloys, bearing metals

F 1/16" ball 60 RedAnnealed copper alloys, thin soft sheet

metals

G 1/16" ball 150 RedPhosphor bronze, beryllium copper, malleable irons.  Upper limit is HRG 92, to avoid possible flattening of ball.

H 1/8" ball 60 Red Aluminum, zinc, lead

K 1/8" ball 150 Red

Bearing metals and other very soft or thin materials.  Use smallest ball and heaviest load that do not give anvil effect.

L 1/4" ball 60 Red

M 1/4" ball 100 Red

P 1/4" ball 150 Red

R 1/2" ball 60 Red

S 1/2" ball 100 Red

V 1/2" ball 150 Red

Aplication for several Materials

Setting for Rod Specimen

Kekerasan Knoop One of MCRO HARDNESS method for small and

thin materials The hardness value provides by pressing a

diamond into the material to be tested under an applied force.

The results of Indentation is between 0.01mm - 0.1mm

The load applied to te material surface is 5 gr to 5 Kg.

The surface must be prepared to be metallographic samples.

Knoop Indentation

Hardness Test Method and Their FormulaHardness Test Method and Their Formula

Relationship of Hardness to Tensile Strength of

MaterialsUTS = 500 BHN (pound/in(pound/in22))

UTS = 500 BHN (MPa)(MPa)

UTS = Ultimate tensile Stress UTS = Ultimate tensile Stress HB = Hardness of BrinellHB = Hardness of Brinell

Hardness is proportional to the tensile strength – but note that the proportionality constant is different for different materials.

Document Number

Document Title

E10 Standard Test Method for Brinell Hardness of Metallic Materials

E18 Standard Test Methods for Rockwell Hardness of Metallic Materials

D785Standard Test Method for Rockwell Hardness of Plastics

ASTM STANDARD

SpecimenTesting Machine

BRINELL TEST for WELDED MATERIALS

Durometer

ULTRASONIC HARDNESS TESTER

Ultrasonic Portable Hardness Tester

Review1. Describe mathematically the formula of Brinell & Vickers from the

basic formula of = P/A .

2. Describe the principle operation of rockwell hardness testing and mention the types of Rockwell Scale and their applications for material testing

3. Jelaskan dengan gambar pengaruh elastisitas bahan terhadap bentuk jejak (indentasi) pada uji kekerasan metoda vickers.

4. The results of hardness testing for a metal using 2 hardness methods are as follows: (by referring to ASTM)(i) Using Vickers method with load 30 kgf, 3 diagonals data provided: the first is 0,527 mm in length, the second is 0,481 mm in length and the last is 0,497 mm in length. (ii) Using Brinell Method with ball indenter 10 mm diameter and the load of 3000 kgf, the 3 indentation data are 4,01 mm, 4 mm and 3.99mm in diameter.Using formula of hardness, calculate for each hardness above. Explain Why the value of hardness is different (have variation) for the same material. Which one is the accurate one