Page 91 - Manufacturing Engineering and Technology - Kalpakjian, Serope : Schmid, Steven R.

Chapter 2 Mechanical Behavior, Testing, and Manufacturing Properties of Materials
carbide ball =l`*l

Shape of indentation
Test lndenter Side view Top view Load, P Hardness number
HV -
*l l*
G
2P
10-mm steel
500 K9
1500 kg
Brinell or tungsten- »l dl+ 3000 kg HB l"D)(D °VD2 ' dz)
Diamond pyramid ~( > L - k
136°
Vickers 1 120 9
A
b
Knoop Diamond pyramid /_/b :_-7T';1___+_l 25 9-5 K9 HK = blip
I '__ L ,l
b/r = 4.oo
Rockwell
A eo kg HRA
C Diamond cone ___ _ 150 kg HRC 100 - 500t
1.6-mm diameter
D t fmm 1oo kg HRD

B . 100 kg HFlB
F _ 60 kg HRF
G steel ban tfmm ` `ii` 150 kg HRG 130 ‘ 500f

E 3.2-mm diameter 100 kg HRE
steel ball

FIGURE 2.13 General characteristics of hardness-testing methods and formulas for
calculating hardness.

distort less than steel balls do. Tungsten-carbide balls are usually recommended for
Brinell hardness numbers greater than 500.

Rockwell Test. Developed by S.P. Rockwell in 1922, this test measures the depth
of penetration instead of the diameter of the indentation. The indenter is pressed
onto the surface, first with a minor load and then with a major load; the difference
in the depths of penetration is a measure of the hardness of the material. Some of
the more common Rockwell hardness scales and the indenters used are shown in
Fig. 2.13. Rockwell superficial hardness tests using the same type of indenters, but
at lighter loads, have also been developed.
Vickers Test. This test, developed in 1922 and formerly known as the diamond
pyramid hardness test, uses a pyramid-shaped diamond indenter (Fig. 2.13) and a
load that ranges from 1 kg to 120 kg. The Vickers hardness number is indicated by
HV. The impressions obtained are typically less than 0.5 mm on the diagonal. The
Vickers test gives essentially the same hardness number regardless of the load, and is
suitable for testing materials with a wide range of hardness, including heat-treated
steels. More recently, test procedures have been developed to perform Vickers-type
tests in atomic force microscopes and nanoindenters, to estimate hardness at pene-
tration depths as low as 20 nm.
Knoop Test. This test, developed by F. Knoop in 1939, uses a diamond indenter in
the shape of an elongated pyramid (Fig. 2.13), with applied loads ranging generally
from 25 g to 5 kg. The Knoop hardness number is indicated by HK. Because of the