Effect of precoating on microstructure of SiC reinforced iron-based coating

The reaction layers consisting of Cr₃Si,Cr₇C₃ and Cr₂₃C₆ were produced on SiC surface by PIRAC technology. The iron-based alloy coating reinforced by precoated SiC particles was prepared by plasma surfacing process with the back-feeding model. The results show that the non-precoated SiC particles dissolve completely in the coating. Massive primary polygonal carbides formed in the upper part,dendrites formed in the middle part and cellular grains generated in the bottom part. The precoated SiC particles distributed in the coating surface,retaining the original shape,and did not dissolve significantly. The region between SiC particles and the matrix could be divided into the interface reaction zone and the transition zone. The interface reaction zone consisted of α-(Fe,Cr) solid solution,massive (Fe,Cr)₇C₃ and (Fe,Cr)₂₃C₆ carbides. The transition zone consisted of the α-(Fe,Cr) solid solution with high Cr content,and it was difficult to expose the microstructure due to its excellent corrosion resistance.