Determination of the Hardness Profile on Heat Treated Steels by Hole Drilling and Indentation Methods

A new approach to determine the hardness profile of superficially heat treated steels is proposed. This method uses the experimental hole drilling technique based on the measurement of the penetration load of the drill for the treated steels with a non negligible hard film thickness and the indentation technique for the case of thin hard films. The thrust measured during a drilling test is reliable to the hardness of the material being tested. The approach using the indentation technique gives a relationship between load, displacement, flow stress and strain hardening exponent. This method is based on minimization of the error between the experimental curve (load-displacement of the indenter) and the theoretical curve, as a function of the mechanical and geometrical properties of the materials studied. Results for carbo-nitriding steels obtained by the standard Vickers micro hardness technique are very close to those obtained by both methods.

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