The influence of geometrical tolerances of Vickers indenter on the accuracy of measured hardness

Abstract

Abstract. This paper reports work carried out to determine the influence of the Pyramidal indenter geometrical errors and tolerances on the accuracy of Vickers hardness measurements. The angle between the opposite faces and line of conjunction of nine indenters were measured by the optical comparator. The influence of the indenter geometry on the hardness accuracy is investigated. Three calibrated reference hardness test blocks were used to check the Vickers hardness test using the nine selected indenters. The results show that the geometrical error of the indenters (specially the angles) considerably affects the accuracy of the hardness measurement. Finite element analysis of the indentation process into metallic test pieces was conducted. Comparison of the experimental results with the numerical findings was discussed. Errors in the experimental values are correlated with measured tolerances in the angles between faces.

Verification of Knoop indenters with a Vickers-addressed optical system

“…In addition, it was found that increasing the cone angle and the tip radius of the indenter entails an increase in Rockwell hardness value [7]. In Vickers hardness, on the contrary, it was found that an indenter with a larger angle, although within the limits allowed by the ISO standard, entails a wider indentation, thus a decrease in hardness value [8], which might exceed permissible values [9]. However for Knoop hardness, few studies on the influence of the indenter geometry are found.…”

A correction method for Vickers indenters squareness measurement due to the tilt of the pyramid axis

“…The influence of indenter characteristics on hardness measurements, in particular for Vickers hardness, is largely reported in literature. It has been demonstrated that different indenters meeting the requirements of the Standards can lead to significantly different hardness measurements, and in particular that an increase in indenter angle entails a decrease in Vickers hardness [1,2]. It was also found that squareness errors and ridge, within the required tolerances, entail small errors in Vickers hardness [3], beyond the influence of the optical system for the evaluation of the indentation impression [4].…”