At the present time micro hardness tests are widely used to determine the hardness of exceedingly thin layers, very small specimens and even separate structural components of alloys. Two types of tests , indentation and scratch, are made to determine micro hardness. The indentation test is based on combining a hardness tester, using a diamond pyramid indenter at low loads, with a metallurgical microscope. Loads from 1 to 200 g are applied. The microhardness number is determined from the formula,
H = 1.8544 (P / d^2 ).
in which P is the load in g, and d is the length of the diagonal in microns.
Microhardness determination based on scratch test involves scratching the surface being tested by diamond under the action of a definite load. The width of the scratch is measured with a special microscope. The Hardness value is defined either as the width of the scratch obtained at a certain constant load or as the load at which the scratch of definite width is obtained.
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