An ultra-low-load penetration hardness tester

An ultra-low-load penetration hardness tester which operates at loads of up to 3 mN with a resolution of 10 mu N is described. It is capable of producing a continuous record of the penetration depth of the indenter and the resolution of the depth measurement is estimated to be 5 nm. A hardness value is deduced from the applied load and the penetration depth, which may be less than 0.1 mu m. The ability of the machine to obtain information on on-load hardness, off-load hardness, elasticity, adhesion and load-dependent effects is demonstrated. The authors describe a study of the properties of a soft metal (indium) and thereby show how the types of measurement obtained are related to conventional microhardness measurements.