Functional properties of a spark plasma sintered ultrafine-grained 316L steel

A micrometric austenitic stainless steel 316L powder was densified by spark plasma sintering. The process parameters were varied over wide ranges and the impact of such variations on sintered materials was studied through the characterization of their microstructures, densities, hardness and corrosion resistance. For comparison with the properties of traditionally cast 316L, all these investigations were also systematically carried out on as cast samples. The sintered stainless steel produced this way was highly densified, with grains of a micrometric size and the forming process did not induce any residual strain gradients as shown by transmission electronic microscopy analysis. The investigation of the corresponding mechanical properties reveals an enhancement of hardness up to twice the value measured on one sample of as cast 316L. This result is in good agreement with the Hall-Petch formalism. Additionally, in the matter of corrosion behavior, fully dense samples display an enhanced passive state in chloride media compared to as cast material. Spark plasma sintering appears to be an interesting alternative elaboration way of ultrafine 316L stainless steel giving materials with high stress resistance, without strain gradients through the volume, and promising functional properties concerning corrosion behavior.