Effect of WC Particle Size and Doping Amount on the Structure and Properties of a WC Reinforced Fe-Mn-Si Shape Memory Alloy (SMA)
Laser Clad onto Stainless Steel
Y. Shao, P. Xu and C.Y. Liu
Fe-Mn-Si/micro-WC and Fe-Mn-Si/nano-WC shape memory alloy (SMA) composite coatings with different WC doping of 8 to 12 wt.% were prepared on the surface of 304 stainless steel substrate by laser cladding with a fibre laser. The WC reinforced composite coatings have a good metallurgical bond with the substrate. The microstructure, phase composition, microhardness and wear resistance of the composite coatings were investigated and the results show that they all have Fe6W6C, γ-austenite phase and ε-martensite phase. The decrease in particle size of WC greatly improved the segregation of components inside the coatings. Although nano-WC refines the structure, the large amount of solid solution of W element hinders the austenite → martensite transformation of Fe-Mn-Si SMA. When the content of nano-WC exceeds 9 wt.%, a small range of segregation occurs in the coating. The average microhardness and wear resistance of the Fe-Mn-Si/nano-WC composite coating are significantly improved due to solid solution strengthening and the second phase strengthening, and the highest microhardness is between 950 to 1000 Hv0.2. The nano-WC doping amount of the composite coating with the best wear resistance was 9 wt.%.
Keywords: Fibre laser, Fe-Mn-Si, tungsten carbide, WC, 304 stainless steel, shape memory alloy (SMA), particle size, solid solution, wear resistance, second phase