Microstructure and tribological properties of FeCrNi-WC medium entropy alloy composite coatings prepared by high-speed laser cladding with different preheating temperatures

To address the wear failure of brake drum surfaces in band brakes caused by high-frequency and heavy-load service conditions and to improve the wear resistance of the brake drum, FeCrNi-WC medium entropy alloy composite coatings were prepared on the surface of brake drum using high-speed laser cladding. Additionally, to prevent coating cracking and enhance microstructural homogeneity, the substrate was preheated at different temperatures (room temperature, 200 degrees C, 300 degrees C, and 400 degrees C). Based on the characterization and testing of the coating's phase structure, forming quality, microstructure, and wear resistance, the results indicated that the primary phase of the coating was an FCC solid solution, WC, W2C, Fe3W3C and Cr23C6, and the change in substrate preheating temperature did not affect the primary phase structure of the coatings. As the preheating temperature increased, the number of defects in the coating gradually decreased. The enhanced dissolution of WC particles in the coatings promoted the precipitation of Fe3W3C eutectic carbides, contributing to coating reinforcement. At a preheating temperature of 300 degrees C, FeCrNi-WC medium entropy alloy composite coating with no cracks and porosity and good forming quality could be achieved. At this temperature, the hardness of the coating reached 662.67 HV0.2, approximately 2.9 times that of the substrate. The excellent comprehensive properties enabled the coating to form a stable and dense tribolayer during sliding wear, resulting in a low friction coefficient accompanied by the lowest wear rate, with wear resistance improved by nearly two orders of magnitude compared to the substrate.