Study On Ni-based Self-fluxing Alloy Coating By Spark Plasma Sintering

In this paper, Ni60 and Ni60_WC Ni-based self-fluxing alloy coatings were prepared on 45 steel substrate by spark plasma sintering. The sintering process of Ni60 and Ni60_WC was optimized by orthogonal test method. The microstructure and properities of the coating were analyzed. The element diffusion of interface was studied by scattering law and preliminary investigated of the bonding mechanism of Nil-based self-fluxing alloy coating/45 steel. The results show that:1. The best sintering process of Ni60 powder is 870℃×65MPa×15min. The phase composition of Ni60 are consist of y-Ni,CrB,Ni3B,Fe3C,Cr7C3, which uniform distribute on theγ-Ni substrate. The microstructure has uniform fine grain, low porosity and no impurity. The hardness and density of Ni60 sintered sample are 64.22HRC,7.713g.cm-3, respectively.2. The best sintering process of Ni60_WC powder is 910℃×65MPa×15min. The phases of Ni60_WC are consist of WC, FeW3C,Cr23C6, Ni3Fe, Ni2B, which improve the wear resistance of samples. The microstructure has some unmelted WC particles on the y-Ni substrate, which enhance the whole properties. The hardness and density are of Ni60_WC sintered sample 70.19HRC,9.786g.cm-3, respectively.3. The best sintering processes of Ni60/45 and Ni60_WC/45 steel are 870℃×65MPa×17 min,910℃×65MPa×15min, respectively. The coating interface has no overall distortion with good combination. The microhardness of Ni60 and Ni60_WC coating are 597.5HVo,3, 968.5HV0.3, respectively. The volumetric wear rate of Ni60 and Ni60_WC coating are 5.43 x 10-2cm3,2.31 x 10-2cm3, respectively. It is showed that it has a distinct white band between coating and substrate with the thickness of 20-25μmand 18-22μm, respectively. The hardness of cross-section ranges from 597.5-209.6HV0.3 and 968.5-225.2HV0.3, respectively and smooth transition. According to microscopic analysis, the interface main diffusion rely on Ni and Fe elements.4. The Ni60 and Ni60_WC coating have the normalizing treatment of 830℃×10min. After normalizing, the width of transition layer has been increased and the element diffusion smoothes the gradient of the micro-hardness. The microstructure of Ni60 and Ni60_WC distribute more uniform with less porosity. The surface wear resistance of Ni60 coating has decreased 14.8% and Ni60_WC coating has increased 51.8%.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 space mechanism. Diffusion coefficient of Fe, Ni elements in the interface falled after rising from coating to substrate...