Impact analysis of electrode materials and EDM variables on the surface characteristics of SS316L for biomedical applications

Abstract

The biocompatibility of the SS316L makes it an alluring alternative for orthopaedic and other biomedical applications. In such applications, surface characteristics of the materials are key considerations for bacterial adhesion at the surface of the metallic implant. Therefore, the current study focuses on the investigation of surface roughness and microhardness of SS316L in the electric discharge machining process using adequate electrode/tool material. Machining is performed with brass, copper, and aluminum electrodes to limit the surface roughness and enhance the microhardness of machining surfaces. Besides this, process variables including peak current, pulse off time, pulse on time and spark voltage are also optimized to obtain superior surface characteristics. Results show that adequate surface roughness of 1.08 μm can be attained with the aluminum electrode while brass electrodes offered increased microhardness of 1270.6 HV of machined surfaces. Microstructural analysis shows that aluminum electrode yields shallow and small-sized craters and few micro-cavities while brass electrode generates high peaks and valleys on the machined surface due to the deep craters, micro cracks, and cavities. The composite desirability function approach suggests that aluminum electrode along with the optimal setting of process variables such as peak current = 25 A, pulse off time = 50 μs, pulse on time = 55 μs and spark voltage = 2 V offers reasonable values of surface roughness 4.09 μm and microhardness 1051.2 HV after trading off.