Effect of Vacuum Environment and Substrate Preheating on Microstructure and Properties of Laser Cladding WC Reinforced Nickel-Based Alloy Coating

Under the condition of vacuum and substrate preheating at 200 ℃, WC reinforced nickel-based alloy coating was prepared on the surface of 45 steel substrate by laser cladding technique. The macro- and micro-morphology, phase composition, hardness and wear resistance of the coating were studied, and compared with those under the condition of direct nitrogen blowing protection in atmospheric environment and substrate unpreheating. The results show that under the condition of vacuum and substrate preheating, there were no cracks and pores in the coating; the structure was uniform and dense, and mainly consisted of cell-like crystals. The phases in the coating were mainly composed of Cr₂₃C₆, Cr₃C₂, γ-Ni and FeNi, and the content of Cr₂₃C₆ hard phase was lower than that under the condition of direct nitrogen blowing protection in atmospheric environment and substrate unpreheating. The average microhardness of the coating was 751.14 HV, about 85.43 HV lower than that under the condition of direct nitrogen blowing protection in atmospheric environment and substrate unpreheating. The stable friction coefficient of the coating was 0.50, and the cross-sectional area of the surface wear scar was about 0.4×10^-3 mm², which were about 23% and 58% lower than those under the condition of direct nitrogen blowing protection in atmospheric environment and substrate unpreheating, respectively, indicating that the wear resistance of the coating was significantly improved.