Influence of process parameters in additive manufacturing of highly reinforced 316L / SiCp composites

Highly reinforced 316 L / SiCp metal matrix composites (MMC) walls have been additively manufactured by Direct Laser Deposition (DLD) using mixtures with different percentages of 316 L stainless steel powder and SiC particles (SiCp). The effect of the percentages of SiCp of up to 80 wt.% and DLD conditions on the geometry, microstructure, and hardness of the fabricated structures have been analyzed. SiC particles react with the molten 316 L steel and chromium and iron carbides are formed, and also graphite flakes and nodules are formed in the matrix. This reaction is also responsible for the dilution of the SiCp, which lose their initial shape and size. The incorporation of higher percentages of SiCp reduces the degradation of the particles as the matrix saturates in Si and C, and also enhances the size of the graphite precipitated phases. The different phases formed help to increase the hardness of the composites, and a maximum value of 1085 HV0.1 was obtained for 40 vol.% of SiCp. Increasing further the amount of SiCp reduced the hardness to values of similar to 890 HV0.1 as the matrix is saturated in carbides and bigger and more brittle graphite precipitates are formed. The characteristics of the manufactured samples for the different reinforcement percentages used and for the different manufacturing conditions have been analyzed. From this study, the DLD processing maps for the 316 L/SiC MMC metal matrix composites with different content of reinforcement have been developed, and the optimal values of laser power, scanning speed, and layer height have been determined, and it has been observed that the optimum fabrication conditions displace to lower scanning speed for higher SiCp contents in the 316 L matrix. Showing that it is possible to manufacture cermets based on steel with lower density and greater hardness than the steel used.