Microstructure And Properties Of Ni60 Alloy Coating By Vacuum Sintering Cladding

In this paper, the Ni60 alloy coating was deposited on Q235 steel substrate by vacuum sintering cladding. The Ni60 alloy coating can be enhanced by adding different contents of WC or TiC particles. In the experiment, the Rockwell hardness tester and the microhardness tester were operated to test the hardness of coating. The abrasive wear test was used to measure the wear resistance of the coating. The corrosion resistance test had been carried out by electrochemical workstation. The results shown that:(1) The influence of process parameters, such as the type of bonder, sintering temperature and holding time, were explored on the performance of coating. The best cladding result of Ni60 alloy coating on Q235 steel plate made by the method of vacuum sintering occurred when epoxy resin was used to bind those materials, with increasing the sintering temperature up to 1080℃ and heating preservation for 10 min. The organization was mainly consisted of γ-(Ni,Fe) solid solution, CrB and Cr23C6. The sintered body had a good density, without obvious porosities and micro cracks, and the HRC hardness of the surface of the coating was 58.3. The microhardness of the coating cross-section, gradient distributed from surface to base material, was ranged from 676 to 220. The abrasive wear loss of the coating reduced significantly, and the coefficient of the wear resistance of the coating was 21.7 times of Q235 steel plate. In addition, the corrosion current density of the coating was lower than that of Q235. The corrosion resistance performance of the coating had been improved significantly.(2) The organization of WC-Ni60 composite coating was mainly consisted of γ-(Ni,Fe) solid solution, while other materials, including WC, CrB, Cr23C6, M6C、Cr4Ni15W, were distributed uniformly in the matrix. The macrohardness of the coating can be improved after adding WC. When the proportion of WC was 25%, the maximum hardness was 1280 HV0.2. With the increase of the amount of WC, the wear resistance increased initially and decreased afterwards. When the proportion of WC was 20%, the abrasive wear loss of the coating reached the lowest value, and the abrasive wear resistance would be the best. The relative wear resistance was about 37 times as better as that of the matrix. The wear mechanism is the slightly plastic cutting and the brittle spalling of hard phase. It is clear that the corrosion resistance of WC-Ni60 coating is better than that of Ni60 coating.(3)The structure of TiC-Ni60 composite coating was very densify, without visible pores and micro-cracks, and the coating was combined well with the Q235 steel substrate. The transition layer of the coating could be saw obviously. The TiC-Ni60 composite coating was mainly composed of γ-(Ni,Fe) solid solution, CrB, Cr23C6 and TiC phase. Within a certain range, the macrohardness of the composite coating increased by increasing the content of the TiC. When the proportion of TiC was 25%, the maximum hardness of coating was 1403 HV0.2. With the increase of the content of TiC, the wear resistance of the composite coating increased initially and then decreased. When the proportion of TiC was 20%, the abrasive wear loss of the coating reached the lowest value, and the relative wear resistance was about 40.6 times of the matrix. It is certain that increasing the amount of TiC can enhance the corrosion resistance of the coating.