Surface modification during hydroxyapatite powder mixed electric discharge machining of metallic biomaterials: a review

Surface modifications play a vital role in the performance of bio-implants. Powder mixed electric discharge machining (PM-EDM), a recently developed advanced machining method, can machine and coat the surface of conductive materials at the same time. Hydroxyapatite is a bio-ceramic with a bone-like composition and excellent biocompatibility. Several coating techniques are used to deposit a bio-ceramic layer on the implant surface; however, hydroxyapatite powder mixed–EDM (HAp-EDM) is an electro-thermal process that can be used for surface coating as well as machining of metallic biomaterials. In this review article, surface characteristics such as surface morphology/topography, micro-hardness, phase analysis, recast layer, elemental composition, corrosion/wear resistance, and biocompatibility of the coated surface of an implant after HAp-EDM have been meticulously reviewed. This review also looks at future research opportunities for the HAp-EDM process to meet the high standards required for biomedical materials and their applications in bio-implant manufacturing.