Micro-indentation hardness test: The practical realization of a standard.

The work described in this thesis forms part of the research programme of the National Physical Laboratory. Started in 1979 at the request of industry, it is directed towards supporting UK industry with the eventual aim of establishing and disseminating standards for the micro-indentation hardness test. The purpose of this thesis is to discuss the many factors affecting the accurate determination of a microhardness number, because although the microhardness test has been used extensively to investigate material properties, little attention is generally paid to the test conditions. The history of microhardness testing over the past fifty years is reviewed and three main problem areas are identified: the machines with which micro-indentations are made, the microscope systems with which they are measured and the materials in which they are produced. Although inextricably linked, the importance of each factor is discussed, some theoretical evidence produced and experimental results obtained to quantify the sources of uncertainty inherent in the test. In addition to the conventional methods of measurement and production, image analysis and scanning electron microscope metrology techniques are assessed and the importance of indentation depth measurement is surveyed. Finally, conclusions are drawn as to further work which is necessary to improve the test and its future importance in the sphere of materials testing