Effect of the Sintering Atmosphere on Vacuum Sintered Metal Injection Molded 316L Stainless Steel

Metal injection molded stainless-steel components are widely adopted in the automotive, biomedical, electronics and fashion industries. Injection molded stainless-steel parts are often sintered on vacuum furnaces to prevent oxidation, contamination and obtain high densities with bright surfaces.

For sintering of stainless-steels on vacuum furnaces, a low partial pressure of inert or reactive gas is commonly adopted to suppress evaporation of volatile alloying elements (i.e. chromium and manganese) and to help removing chemical residual from binders and lubricants. During sintering, the gaseous atmosphere reacts with the surface of the steel influencing its final mechanical and corrosion properties.

In this experiment, we investigated the effect of different sintering atmospheres (i.e. partial pressure of pure argon or pure hydrogen) on 316L parts injection molded using two feedstock formulations, the first one based on a water-soluble binder system, the second one based on a catalytic binder system.

The microstructures of the sintered samples were analyzed and compared through optical microscopy. The carbon and oxygen contents were determined using a Carbon/Sulphur analyzer and an Oxygen/Nitrogen analyzer. Moreover, the final densities of the samples were measured by using the Archimedes’ principle after impregnation. Finally, the corrosion resistance properties were assessed with neutral salt spray testing.