Microstructures evolution and properties of titanium vacuum sintering on metal injection molding 316 stainless steel via dip coating process

Abstract

Enhancing the surface coating of 316 L stainless steel, fabricated via metal injection molding, is crucial for its application in cost-effective, mass-produced components. This study investigated the titanium coating on 316 L stainless steel to address its limitations in mechanical performance. Titanium was coated on the 316 L stainless steel via a dip coating process, followed by vacuum sintering at temperatures of 1100 °C, 1150 °C, and 1200 °C. The optimal mechanical properties were achieved with a 100 μm thick coating sintered at 1200 °C, which exhibited uniformity and good bonding strength. The microstructure results demonstrated an average yield strength of 342.63 MPa and a polarization impedance of 968.48 Ω·cm². Electron probe microanalysis confirmed the uniform diffusion of titanium into the stainless steel substrate, forming intermetallic phases such as Fe₂Ti and NiTi. In addition, this study conducted a heat treatment process for the as-coated specimens. It was found that annealing at 750 °C for 4 h oil quenched and a 550 °C three-hour aging treatment the polarization impedance increases to 1243.3 Ω·cm² without compromising the yield strength. These findings indicate that the titanizing process enhances the mechanical properties of 316 L stainless steel, making it more suitable for demanding applications.