激光熔覆NiCrBSi/Ag复合涂层 结构及空间摩擦学性能

目的 提高钛及钛合金的空间摩擦学性能，拓展钛及钛合金在空间技术领域的应用范围。方法 用激光熔覆技术在纯钛基材表面制备了NiCrBSi/Ag复合涂层。用X-射线衍射仪、扫描电镜和高分辨透射电镜分析涂层的物相组成、显微组织结构和晶体结构。用空间摩擦学实验系统对NiCrBSi/Ag复合涂层在真空、原子氧和紫外辐照三种模拟空间环境以及大气环境下的摩擦学性能进行系统的研究。采用扫描电镜和能量色散光谱仪对摩擦测试后NiCrBSi/Ag复合涂层的磨痕形貌和对偶不锈钢钢球的磨痕形貌及元素面分布进行分析。深入探讨NiCrBSi/Ag复合涂层在三种模拟空间环境及大气环境下的磨损机理。结果 在纯钛基材表面通过激光熔覆制备的NiCrBSi/Ag复合涂层主要物相组成为NiTi、Ni3Ti、Cr2Ni3、Cr3Si、TiB2、Cr-Ni-Ti-Fe、Ag相，显微结构主要为等轴晶和枝状晶组织。复合涂层具有较高的显微硬度，涂层截面平均显微硬度约为830HV0.2，约是钛基材硬度的4.4倍。复合涂层在真空、原子氧和紫外辐照模拟空间环境下的摩擦系数和磨损率均小于大气环境下的值。在三种模拟空间环境下，相对于纯钛基材，复合涂层的磨损率约小2个数量级。复合涂层在真空、原子氧和紫外辐照模拟空间环境下的磨损机理为粘着磨损和磨粒磨损，在大气环境下的磨损机理主要为磨粒磨损。结论 NiCrBSi/Ag复合涂层可以显著提高纯钛基材在真空、原子氧和紫外辐照三种模拟空间环境以及大气环境下的摩擦学性能。

Microstructure and Space Tribological Properties of NiCrBSi/Ag Composite Coating Prepared by Laser Cladding

The work aims to improve the tribological properties of titanium and titanium alloys in space environments and expand the application range of titanium and titanium alloy in space technology. NiCrBSi/Ag composite coating was prepared on pure titanium substrate by laser cladding technology. The phase composition, microstructure and crystal structure of the coating were analyzed by X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy. The tribological properties of NiCrBSi/Ag composite coating under high vacuum, atomic oxygen and ultraviolet irradiation in simulated space environment and atmospheric environment were studied by space tribology experiment system. The wear marks of NiCrBSi/Ag composite coating and the antithesis stainless steel ball were analyzed by SEM and EDS. The wear mechanism of NiCrBSi/Ag composite coatings in three simulated space and atmospheric environments was investigated. The main phases of NiCrBSi/Ag composite coating prepared by laser cladding on the surface of pure titanium substrate were NiTi, Ni3Ti, Cr2Ni3, Cr3Si, TiB2, Cr-Ni-Ti-Fe and Ag. The microstructure of composite coating was mainly composed of equiaxed crystal and dendritic crystal. The composite coating had high microhardness and the average microhardness of coating section was about 830 HV0.2, which was about 4.4 times of that of titanium substrate. The friction coefficient and wear rate of the composite coating under high vacuum, atomic oxygen and ultraviolet radiation were smaller than those under atmospheric environment. The wear rate of composite coating in three simulated space environments was about 2 orders of magnitude smaller than that of pure titanium substrate. The wear mechanism of composite coating under high vacuum, atomic oxygen and ultraviolet radiation was adhesive wear and abrasive wear, while the wear mechanism in atmospheric environment was abrasive wear. NiCrBSi/Ag composite coating can significantly improve the tribological properties of pure titanium substrate under high vacuum, atomic oxygen and ultraviolet irradiation space environments.