Ultra-Micro Hardness Tester Measuring Displacement of Indentation

Abstract

A new type of ultra-micro hardness tester has been developed in order to obtain precise indentation hardness of thin films and brittle materials. A differential coil with an accuracy of 0.01 μm is used in measurement of indentation depth instead of width. Electromagnetic force generated by applying an electric current to force coil is utilized for loading to a specimen, and so indentation hardness at a load of 9.8 × 10^-5 N {10 mgf} can be obtained. Indentation test is automatically performed according to the program in microcomputer, and increasing load and indentation depth can be instantly recorded during the test. Use of microcomputer enables value of load and loading speed to be set over a wide range. A new method of finding out the surface of specimen is devised and experimentally confirmed. The indentation test in a few materials shows that the displacement of the indenter during loading is divided into the elastic and plastic ones with a high accuracy.