Improving Microhardness of AISI 316L Stainless Steel by Ball Burnishing- Optimization by BOX-BEHNKEN Model

Abstract

In the field of mechanics and biomaterials, particular attention is directed to the finishing step of pieces because it conditions several properties of materials, namely surface quality and microhardness. The mechanical surface treatment (TMS) by burnishing is one among the most competent finishing operations aimed toward improving the characteristics of surface and also the lifetime of components. Although this treatment is extremely effective, but it is very necessary to choose the appropriate combination of process parameters to realize better results. This work aims to improve, by ball burnishing, the microhardness of 316L stainless steel used for the manufacture of biomedical hip prostheses. This property is vital because it directly influences other final properties such as tensile strength, wear resistance and fatigue life. The response surface method based on Box-Behnken model is followed for experiments and an empirical model expressing the relationship between microhardness and process parameters (burnishing force, feed rate, and ball diameter ) is developed. The optimal regime for maximum hardening is also established. The results show that burnishing treatment, carried out on a flat surface, makes it possible to significantly hardening the surface of 316L stainless steel by obtaining a greater value by up to 67% compared to the untreated surface. Scanning electron micrographs show a very thin surface layer containing grains deformed plastically in the burnishing direction.