Study of the correlation between Rockwell and Vickers hardness

Hardness measurement of metallic materials at its high levels is usually performed using Rockwell (HRC) or Vickers (HV) methods. The purpose of this study is to investigate the correlation between Rockwell and Vickers hardness values. Analysis of technique gives the following general formula: HV = (A/(B – HRC))². This formula describes well the high hardness region at A = 4400 MPa^1/2 and B = 110. Comparison with the tables of ASTM A370-20 and ASTM E140-12b standards yields A = 4700 MPa^1/2 and B = 117. In both cases the formulae tend to the borders of the scatter band of available data. The relative middle of the scatter band corresponds to A = 4500 MPa^1/2 and B = 113. The difference between the three relationships increases with increasing hardness and reaches four units at the level of 70 HRC. This means that numeric values of the A and B coefficients are to be determined more specifically for separate groups of materials. Obtained results can be used for improvement of the technique of determination of hardness of metallic materials and for comparison of the values of hardness determined by different methods.

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