Influence of γ-alumina coating on surface properties of direct metal laser sintered 316L stainless steel

Direct metal laser sintering (DMLS) is an additive manufacturing technique that enables the production of customized and complex shaped stainless steel products. Application of DMLS parts to critical sectors requires enhanced surface properties. Although extensive research has been undertaken by many investigators on gamma-alumina coating on conventionally processed SS 316L, there has been no significant exploration of the properties of SS 316 L processed through DMLS process with and without coating. In this study, an attempt has been made to coat gamma-alumina ceramics over 316L SS substrate and report its effects. gamma-alumina synthesised using sol-gel technique was examined through Fourier-Transform Infrared Spectroscopy and X- Ray Diffractometer. The coating were 28-36.77 mu m thick and had amorphous structures. Characterization on coated substrate displayed a 33.87% increases in hardness and 81.91% increase in roughness. The water contact angle of the coated substrate exceeded bare substrate measurements by over 340. I-corr value of 0.0967 for coated substrate confirmed the anti-corrosive behaviour, which was found to be very much an essential requirements for this study. Compared with conventional processed SS 316L, the performance of DMLS SS 316L, the performance of DMLS SS 316L bare substrate and coated substrate are mainly governed by properties such as porosity, laser scanning effect, in build residual stress and surface finish. The development of uniform and adherent coating of gamma-alumina acts as a mechanical barrier for enhancement of the surface properties which will enlighten the research and applications in the fields of biomedical, aerospace and automobile industries.