| At present,Ni-based alloy powders have a wide range of applications in improving wear resistance and corrosion resistance of mechanical parts due to their good wettability,corrosion resistance and oxidation resistance,as well as excellent wear resistance and low cost.NiCrBSi is a typical Ni-based alloy,and coatings prepared using the alloy powders are widely used in a variety of wear and corrosion environments.Because the hardness of NiCrBSi is lower than that of ceramic materials,it can meet the requirements in common wear environment;however,it is difficult to meet the requirements of high-load service environment.Hard particles such as carbides and oxides are often added as reinforcing phases to the NiCrBSi coating to improve the performance of the NiCrBSi coating.Previous studies have found that nanocrystalline TiN coatings can be prepared by reactive plasma spraying.In this paper,nano-TiN was used as the strengthening phase to prepare nanocrystalline TiN reinforced NiCrBSi composite coating by reactive plasma spraying.The microstructure and phase of the coating were analyzed by AFM,SEM,TEM and XRD,and the wear resistance and corrosion resistance of the coating were studied.In order to further improve the performance of NiCrBSi-TiN composite coating,heat treatment was carried out at 600?,700?,750?and 800?,and its microstructure,friction and wear properties and corrosion resistance were analyzed.Finally,the NiCrBSi-TiN composite coating was compared to a WC-reinforced NiCrBSi coating.The results show:(1)The NiCrBSi-TiN composite coating consists mainly of phase phases such as?-Ni,Fe Ni3and Cr1.12Ni2.88and TiN phase.Compared with NiCrBSi,the hardness of NiCrBSi-TiN composite coating is increased but the toughness is decreasing.The wear performance and corrosion resistance are significantly improved.(2)Compared with the original coating,the phase composition of the coating after heat treatment changes,the strengthening phase such as Ni17Si3precipitates,and TiN partially decomposes to form TiN0.3.After the temperature reaches 750°C,the phase interface between the TiN phase and the Ni-based solid solution reacts and diffuses.With the increase of heat treatment temperature,the hardness,wear resistance and corrosion resistance of NiCrBSi-TiN composite coatings increased first and then decreased.When the heat treatment temperature is 700°C,the performance of NiCrBSi-TiN composite coating is optimal.(3)Compared with the NiCrBSi-WC composite coating,the NiCrBSi-TiN composite coating has a higher average micro-hardness and a higher wear resistance.Further,the bonding between the WC reinforcing phase and the Ni-based solid solution phase in the NiCrBSi-WC composite coating is not tight,and intergranular cracks exist.However,TiN is synthesized by in-situ reaction and tightly combined with Ni-based solid solution in the NiCrBSi-TiN composite coatings.Therefore,TiN is more suitable as a reinforcing phase of the NiCrBSi coating than WC. |
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