CrB颗粒增强MMC涂层的组织及其耐磨机理

用超音速电弧喷涂方法制备CrB颗粒增强的MMC涂层,利用金相显微镜、扫描电镜(SEM)及电子探针(EPMA)分析方法,对涂层的微观组织及微区成分进行分析;在实际循环流化床锅炉水冷壁上进行现场试验以检测涂层的耐高温冲蚀磨损性能,对涂层冲蚀表面的微观形貌进行分析,研究涂层的耐磨机理。结果表明:涂层具有复合材料的典型层状组织特征,金属基体在涂层中连续分布;增强颗粒主要为Cr的硼化物和Cr的氧化物。硬质相颗粒均匀弥散分布在涂层中,起到强化作用,并可阻挡冲蚀划痕的扩展,减缓了涂层金属基体受磨损的进程;塑、韧性较好的金属基体可缓冲冲蚀粒子对硬质相颗粒的冲击,使涂层具有优良的耐冲蚀磨损性能。

Microstructure and abrasion resistance mechanism of CrB particles reinforced MMC coating

The CrB particles reinforced MMC coating was prepared by high velocity arc spraying(HVAS) method.Through a series of experiments,including metallograph,SEM and EPMA,the microstructure and composition of the coating were analyzed in details.The high temperature abrasion resistance as well as its mechanism of the CrB coating was studied through field test,which was done by depositing the coating on the surface of the water-wall tubes in a circulating fluidized bed boiler.The results show that the microstructure of coating is typical compact structure with layer upon layer,and each layer is composed of successive metal matrix.The hard particles are mainly compounds of boron and chromium and oxide of chromium,scattering evenly and dispersedly in the coating,which can reinforce the coating and play a nail's role in hindering the movement of the abrasion particles.On the other hand,the metal matrix with good ductility and toughness can buffer the impact caused by the abrasion particles.Therefore,the abrasion rate of the coating can be greatly slowed down and the coating will have excellent abrasion resistance.