Effects of Sintering Conditions on the Mechanical Properties of Metal Injection Molded 316L Stainless Steel

In this work, tensile and fatigue properties of the metal injection molded 316L stainless steel were studied with the variation of sintering conditions. It was found that increasing sintering temperature and time resulted in a decrease in the porosity along with an increase in the grain size. With decreasing porosity, tensile strength and elongation increased, while yield strength maintained constant, which was attributed to the balanced effects of decrease of porosity and grain coarsening. Tensile strength and elongation were found to be largely dependent on the porosity rather than on the grain size since the fracture occurred mainly by microvoid growth and coalescence. A quantitative analysis on the yield strength was tried by considering the classical Hall-Petch equation and mechanistic models for yield strength of porous materials. The fatigue crack growth resistance at low ΔK level was not largely decreased when the porosity was increased up to 8%, but was significantly decreased when the porosity was increased to 17%. It was discussed in relation to the intrinsic nature of pore morphology and the extrinsic nature of crack closure.