钛表面激光熔覆NiCr-Ag复合涂层结构及空间摩擦学性能研究

Microstructure and Space Tribological Properties of Laser Clad NiCr-Ag Composite Coating on Pure Ti Substrate

摘要:

利用激光熔覆技术在钛基材表面制备了NiCr-Ag复合涂层。用XRD、SEM和HRTEM分析了涂层的组成和组织结构,利用空间摩擦学系统对复合涂层在三种模拟空间环境(高真空、原子氧和紫外辐照)以及大气环境下的摩擦磨损性能进行了系统的研究。采用SEM和EDS对磨损后复合涂层和对偶钢球的形貌和元素面分布进行了分析,揭示了复合涂层在模拟空间环境及大气环境下摩擦磨损失效机理。结果表明：复合涂层在大气环境条件下的摩擦磨损性能优于在三种模拟空间环境下的摩擦磨损性能；真空下的辐照对复合涂层的摩擦磨损性能有显著的影响,辐照会增加涂层表面氧化；复合涂层在高真空、原子氧和紫外辐照模拟空间环境下的磨损机理为较严重的粘着磨损、磨粒磨损和塑性变形,在大气环境条件下的磨损机理主要为磨粒磨损。

关键词:空间摩擦; 激光熔覆;磨损机理; 结构; 激光原位反应

Abstract:

The composite coating NiCr-Ag was successfully prepared by lase clad on substrate of pure Ti in order to enhance space tribological properties of pure Ti, with hard phase NiCr as the reinforcing agent and Ag as the primary lubricating fillers. The composition and microstructure of the fabricated composite coating were investigated by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), and high-resolution transmission electron microscopy (HRTEM). Furthermore, the space tribological properties were systematically evaluated by a ball-on-disc tribometer against AISI-52100 ball counterpart under simulated space environment including atomic oxygen (AO), ultraviolet irradiation (UV), and high vacuum (VC) in comparison with that in atmospheric environment (AR) through the space tribological test system. The results show that the composite coating has better tribological properties in atmospheric environment than those in simulation space environment. Findings indicate that the vacuum (without any moisture or hydrocarbons) and intense radiation in the space environment would induce severe oxidation on the surface of the coating, making the enhancement of the coating weak and the lubrication effect deteriorated. The wear mechanism is abrasive wear under atmospheric environment. Adhesion wear and plastic deformation are the predominant wear mechanism under space environment as peeling pits and transferred Ni, Cr, and Ti could be found on the worn surface and the surface of the counterpart, respectively.

Key words:space tribology; laser cladding; wear mechanism; microstructure; laser in situ reaction.