磁悬浮列车闸片用硬质涂层的相结构及其性能研究

为改善磁悬浮列车闸片的制动性能,延长使用寿命同时降低生产成本。采用超音速喷涂工艺,在磁浮列车制动用闸片基体表面分别制备了WC-12Co和Cr_3C_2-25NiCr两种硬质涂层。硬质涂层的性能不仅与硬质相晶粒的大小有关,而且还与相组成及相转变密切相关。本研究利用扫描电子显微镜(SEM)、氧氮分析仪、万能试验机和显微硬度计等测试表征方法,分别对涂层的显微组织、氧化物含量、结合强度和显微硬度等结构和力学性能进行分析探究。从热力学的角度出发,对涂层中碳化物的生长条件及相变过程进行了讨论。结果显示,在本工艺参数条件下,超音速喷涂制备的WC-12Co和Cr_3C_2--25NiCr硬质涂层显微组织致密,孔隙率小于1%,涂层中的氧含量分别为0.78%和1.25%,平均结合强度分别为75.2 MPa和73.8 MPa,平均显微硬度分别为1355.8HV_1和1160.5HV_1。因此,通过材料设计的热力学分析,优化喷涂工艺,有利于高性能硬质陶瓷涂层的研制。

Investigation on Phase Structure and Properties of Hard Coatings Used in Maglev Train Brake Shoes

In order to improve the braking performance of maglev train brake shoes, and prolong the service life and reduce the production cost at the same time. The WC-12Co and Cr₃C₂-25NiCr hard ceramic coatings were prepared on the brake shoes substrate of maglev train by means of supersonic flame spraying. The performance of hard coating is not only related to the size of hard phase grain, but also closely related to phase composition and phase transformation. The microstructure, oxygen content, bonding strength and microhardness of the coatings were characterized and analyzed by means of scanning electron microscopy (SEM), oxygen-nitrogen analyzer, computer controlled hydraulic universal testing machine and microhardness tester, respectively. The results show that the microstructure of WC-12Co and Cr₃C₂-25NiCr coatings prepared by supersonic spraying is compact, with the porosity of 1% and the oxygen content of 0.78% and 1.25%, respectively. The average bonding strength were 75.2 MPa and 73.8 MPa, respectively, and the average microhardness were 1355.8 HV₁ and 1160.5 HV₁, respectively. Therefore, through thermodynamic analysis of material design and optimization of spraying technology, it is beneficial to the development of high performance hard ceramic coating.