HVOF制备的微纳米结构WC-12Co涂层组织结构与抗空蚀性能

本文中采用HVOF工艺制备了二种微纳米结构及一种普通微米WC-12Co金属陶瓷复合涂层,并采用SEM、XRD等分析了涂层的显微形貌和组织结构;测量了涂层的显微硬度、孔隙率及开裂韧性;采用超声振动空蚀装置研究了涂层的抗空蚀性能,探讨了涂层空蚀机理.结果表明:由亚微米与纳米WC-12Co组成的微纳米结构涂层孔隙率最低,组织最细小;虽然HVOF制备的微米WC-12Co涂层中WC基本上没有产生氧化脱碳,但是在二种微纳米结构WC-12Co涂层中WC不同程度地产生氧化脱碳,生成W₂C、W及Co₆W₆C等物相;由亚微米与纳米WC-12Co组成的微纳米结构涂层显示了最优异的抗空蚀性能,空蚀率仅为微米涂层的1/3,其涂层抗空蚀性能提高的根本原因在于涂层中同时存在亚微米和纳米尺寸的WC、W₂C、Co₆W₆C高硬度颗粒及一定量的Co、W韧性金属,由此提高了涂层的硬度和开裂韧性,延缓了微裂纹的产生与扩展.

Structures and Resistance of Cavitation Erosion Micro-nanostructured

Two micro-nanostructured and a conventional WC-12Co cermet coatings were deposited by High Velocity Oxy-Fuel spray (HVOF), and the morphologies and structures of the coatings were analyzed by SEM, XRD. Porosity, microhardness and fracture toughness of the coatings were measured. Resistance of coatings to cavitation erosion was studied by ultrasonic vibration cavitation equipment and the cavitation mechanisms were explored. Results show that for the micro-nanastructured WC-12Co coating composed of submicro and nano WC had the lowest porosity and the densest microstructure in comparison with other two WC-12Co coatings. Decarburization of WC occurred in some degree and W₂C, W and Co₆W₆C phases formed during spraying micro-nanostructured WC-12Co powders although obvious decarburization was not observed for conventional WC-12Co powder. It is found that the micro-nanostructured WC-12Co coating made up of submicro and nano WC exhibited the best cavitation erosion resistance and the erosion rate was approximately one third that of conventional one. The enhanced cavitation resistance of the micro-nanostructured WC-12Co coating was attributed to the presence of submicro and nano sized, high microhardness WC, W₂C and Co₆W₆C particles and tough Co and W in the micro-nanostructured HVOF WC-12Co coating. This increased the coating microhardness and fracture toughness and made it difficult for the formation and propagation of the microcracks.