Prediction of hardness–depth profile from indentations at surface of materials

Abstract

Surface treatments are used to increase the resistance of the surface of mechanical parts. Unlike thin films, surface hardened materials may cover several tenths of millimetres in depth. The effectiveness of such treatments is studied by analysing the hardness–depth profile. In this paper, the authors describe a method to evaluate the hardness profile with depth based on the estimation of the contribution of deeper zones of the hardened material to the hardness of the surface through the practice of a series of indentations on the surface with increasing loads. This model allows estimating the hardness of virtual layers through a step by step calculation process at increasing depths under the surface of the material. The model was satisfactorily tested on stainless steel previously surface treated through ion nitriding with a duplex process consisting in ion nitriding followed by the irradiation with high energy short duration plasma beams of argon.