Microstructure and tensile properties of in situ polymer-derived particles reinforced steel matrix composites produced by powder metallurgy method

In this study, steel matrix composites were fabricated using 316L/ polycarbosilane (PCS) system via a novel semi powder metallurgy method including solution-assisted wet mixing and spark plasma sintering (SPS). PCS/316L powders could be obtained by coating the starting 316L powder with PCS, then followed by SPS. After sintering, M7C3 and iron silicide dispersion are in situ formed by the reaction between the 316L and PCS-derived SiC phase, and dispersed along the grain boundaries of the austenitic matrix forming a network structure and refining the microstructures of the metal matrix. Tensile tests revealed that the yield strength (YS) and ultimate tensile strength (UTS) are improved with increasing PCS content, within certain range of PCS content (0-3 wt%). The 316 L-3 wt% PCS composite exhibits a YS of 526 ± 21 MPa and a UTS of 898 ± 9 MPa, representing a 49.4% and 38.6% improvement, respectively, when compared to pure 316L. The enhanced tensile properties of the composite is due to the network structure, refined microstructures and solid solution effects as well as good compatibility between M7C3 and austenitic matrix. However, with increasing amount of reinforcements above 3 wt%, a slight decreased strength is observed.