Study On Ni-based Self-fluxing Alloy Coating By Aerobic Sintering

Ni60 and Ni60_WC self-fluxing alloy coating were sintered on 45 steel substrate in the box-type furnace with aerobic state. The sintering process of Ni-based self-fluxing alloy coating was optimized by orthogonal test method. The microstructure and properities of the coating were analyzed. Ni-based self-fluxing alloy coatings'bonding mechanism was investigated based on the coatings's linescanning. Results show that:1. Ni60 self-fluxing alloy's best sintering process is 1000℃×15min and with tapping temperature to 400℃.The Ni60 self-fluxing alloy's microstructure is that Fe3C,Cr7C3, CrB, Ni3B etc are distributed in y-Ni substrate, with tiny grain and low pore ratio;the density of Ni60 self-fluxing alloy is 7.64g/cm3, and the hardness is 56.96HRC.2. Ni60_WC self-fluxing alloy's best sintering process is 1000℃×15min and with tapping temperature to 400℃.The Ni60_WC self-fluxing alloy's microstructure is that WC, (Cr) 23C6, Co3W3C, etc are distributed inγ-(Fe, Ni) substrate, with low pore ratio and serious WC segregation;the density of Ni60_WC self-fluxing alloy is 9.23g/cm3, and the hardness is 63.22HRC.3. The best sintering process of 45/Ni60 coating and 45/Ni60_WC coating are 1000℃x 15min, with a tapping temperature to 400℃and 1000℃×17min, with a tapping temperature to 400℃.The coating interface has white band with good combination The microhardness of Ni60 and Ni60_WC coating are 545HV0.1,918.4HV0.1, respectively. The volumetric wear rate of Ni60 and Ni60_WC coating are 4.35×10-3cm3/mim,2.45×10-3cm3/min, respectively. It is showed that it has a distinct transition layer between coating and substrate with the thickness of 0.35mm and 0.3mm, respectively. The hardness of cross-section range from 545HV0.i-219HV0.1 and 918.4HV0.i～220HV0.1, respectively.4. The Ni60 and Ni60_WC coating have the normalizing treatment of 830℃×10min. After normalizing, the average microhardness of 45/Ni60 coating and 45/Ni60_WC coating increased by 124.3HV0.1 and 150.8HV0.1, while the wear rate decreased by 20.7% and 26.5%, respectively.5 The diffusion process of Ni-based self-fluxing alloy and 45 steel coating include three stages:the physical contact, the activation and diffusion of contact surface and the formation of coating. Diffusion mechanisms mainly involve vacancy mechanism and transposition mechanism, and B,C alloy elements'diffusion is vacancy mechanism, and the diffusion of Ni, Fe elements is transposition mechanism.The line scanning showed that Fe element spread to coating direction, and Ni,B,C element spread to the direction of matrix.