Relationship of hardness to load on the indentor and hardness with a fixed diagonal of the indentation

For high-hardness materials, particularly for ceramics, the relationship of hardness to load is revealed very strongly. An equation is proposed for conversion of Vickers hardness from one load to another: $$HV = HV_1 left( {frac{P}{{P_1 }}} right)^{1 - 2/n}$$ where HV and HV₁ are the hardness with loads on the indentor of P and P₁ respectively. The parameter n is determined from the equation P = const dⁿ, where d is the indentation diagonal. The parameter n may also be determined on the basis of a normalized curve of the value of HV/E (E is Young's modulus). The physical nature of the relationship of hardness to load is discussed and the hardness (HV_{d_f }) is introduced with a fixed indentation diagonal d_f (and not with a fixed load) calculated using the equation $$HV_{d_f } = HVleft( {frac{d}{{d_f }}} right)^{2 - n}$$ . The introduction of (HV_{d_f }) makes it possible to unify measurement of microhardness for different materials at different temperatures. Curves are given simplifying conversion of hardness from one load to another and determination of the hardness (HV_{d_f }) .