Effect of surface treatment on powder injection molding performance of 316L stainless steel powders

The 316L stainless steel powder injection molding feedstock was prepared by melt mixing with polyethylene glycol/epoxy resin (PEG-EP) as the powder surface modifier and polyformaldehyde resin (POM) as the binder system. The sintered 316L samples were obtained by nitric acid catalytic degreasing and sintering. The encapsulation effect of PEG-EP on 316L stainless steel powders and the influence of PEG-EP surface treatment on the properties of 316L stainless steel powder injection molding feedstock and the sintered specimens were studied by Fourier transform infrared spectroscope, scanning electron microscope, contact angle measuring instrument, rotary rheometer, universal material tester, metallographic microscope, carbon-sulfur analyzer, and microhardness meter. The results show that, PEG-EP are successfully coated on the surface of 316L steel powders, which improves the interface compatibility between 316L stainless steel powders and POM and enhances the feedstock fluidity, the mechanical properties of raw billets, and the mechanical properties and hardness of the sintered samples. When the PEG-EP mass fraction is 0.662% and the powder loading (volume fraction) is 63%, the tensile strength, fracture elongation, and bending strength of the 316L injection raw billets are 10.57 MPa, 8.38 %, and 21.24 N·(mm²)⁻¹, respectively. The grain size, the maximum tensile strength, and the Vickers hardness of the sintered sample are 50.8 μm, 688 MPa, and 151 HV, respectively, leading to the best comprehensive performance.