激光熔覆NiCr-ZrB_2复合涂层结构及高温摩擦学性能

Microstructure and High Temperature Tribological Properties of NiCr-ZrB_2 Composite Coating

利用激光熔覆技术在纯钛表面制备了NiCr涂层和NiCr-ZrB2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了涂层的组成、组织结构和晶体结构.在SRV-IV摩擦磨损试验机上对NiCr-ZrB2复合涂层从20到500℃的摩擦磨损性能进行了测试.结果表明:NiCr-ZrB2复合涂层的主要物相组成为[Ni,Ti]固溶体、Cr2Ti、ZrB2、ZrB、Ni3Cr2、Ti2Cr、TiB2和TiB;涂层厚约0.7～1.0 mm;涂层平均硬度约为HV0.21000,是纯钛基材的5.3倍;NiCr-ZrB2复合涂层的摩擦系数和磨损体积随温度的增加而减小,高温耐磨性能相对于钛基材提高约1个数量级;NiCr-ZrB2复合涂层的磨损机理为磨粒磨损和黏着磨损,高温下伴有氧化磨损和摩擦抛光现象.

NiCr coating and NiCr - ZrB2 composite coating are prepared on pure Ti substrate by the laser cladding. The composition and microstructure of the coatings are analyzed by X - ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy. The tribological properties of NiCr coating and NiCr - ZrB2 composite coating are evaluated on a SRV - IV tribo - tester at elevated temperatures （ 20 - 500 ℃ ）. The results show that 1NiCr - ZrB2 composite coating is mailnly composed of [Ni, Ti3, Cr2Ti, ZrB2, ZrB, Ni3Cr2, Ti2Cr, TiB2 and TiB phases. The NiCr- ZrB2 composite coating is metallurgically bonded to the titanium substrate, and the coating contains dentritic and block - like microstructure. In addition, the NiCr- ZrB2 composite coating has a microhardness of ca HV0.21000 and with thickness of 0.7 - 1.0 mm. The friction efficient and wear volume of the NiCr - ZrB2 composite coating decrease with increasing temperature. The NiCr - ZrB2 composite coating has higher wear resistance than that of titanium substrate. The wear mechanisms of NiCr - ZrB2 composite coating at elevated temperatures are abrasive wear and adhesive wear.