Microstructure evolution, mechanical and abrasive wear properties of NiCrSiB-SiC composite coatings prepared on 16Mn low-carbon steel by Ni-based alloy catalyzed SiC decomposition

In this study, NiCrSiB-SiC composite coatings were prepared on 16Mn low-carbon steel by vacuum cladding technology using SiC and NiCrSiB mixed powders as raw materials for enhancing their wear resistance. The effects of different content of SiC particles on the microstructure evolution, mechanical and abrasive wear properties of the coatings were investigated. The results showed that SiC particles in all the NiCrSiB-SiC composite coatings with different SiC contents were completely decomposed into C and Si under the catalysis of Ni-based alloy. The out-diffused Si into the coating mainly led to the formation of the Ni3Si eutectic phase, while the out-diffused C introduced M7C3, M3C2, M2(C, B) and other hard phases. Besides, C also diffused to the substrate, leading to a carburizing effect, which remarkably enhanced the mechanical properties of the substrate. In the NiCrSiB-SiC composite coatings with high SiC content, the decomposition of SiC led to the remaining graphite phase. However, once the concentration of SiC was over high, excess graphite would deteriorate the compactness and adhesion of the coating, weakening its wear performance. The nanoindentation and abrasive wear experiments revealed that the composite coating with 5 wt% SiC particles had lower elastic modulus (E), higher hardness (H), H/E, and H3/E2, and its wear volume was only 1/10 of that of the substrate, indicating the best mechanical and wear properties. The excellent wear performance can be attributed to the combination of the in-situ formed carbides and borides hard reinforcing phases and the tough coating matrix composed of Fe and Si dissolved γ-Ni and Ni3Si eutectic phase.