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设计30wt%~70wt%不同Mo含量的Mo-Ni混合粉末,通过添加少量ZrO2形成梯度复合合金粉末,采用激光直接沉积技术在3Cr2W8V钢板上制备Mo-Ni-ZrO2高温耐磨复合合金梯度涂层。利用金相显微镜、显微硬度计、SEM、能谱仪及XRD等对制备梯度涂层的组织结构、裂纹与气孔消除、相组成及其硬度等进行了研究。结果表明:在Mo-Ni系复合合金梯度涂层中,由于Mo在激光作用下易氧化为MoO_3,MoO_3受热易挥发,在熔池中未能及时逸出,因此,涂层在50wt%Mo梯度层处开始出现裂纹和气孔,其显微硬度平均值为287.29;在Mo-Ni-ZrO2系梯度涂层中,添加ZrO2后,50wt%Mo梯度层处的裂纹和气孔明显减少,该涂层中主相为MoNi及强化相Mo1.24Ni0.76、Ni3Zr,还有少量MoO_3,其显微硬度平均值为477;ZrO2具有良好的消除Mo-Ni高温复合合金梯度涂层裂纹气孔缺陷与增强梯度涂层硬度的作用。
Mo-Ni mixed powders with different Mo content of 30wt% ~ 70wt% were designed. A small amount of ZrO2 was added to form gradient composite alloy powders. The laser direct deposition technique was used to prepare Mo-Ni-ZrO2 high temperature wear-resistant composite alloy gradient coatings on 3Cr2W8V steel. The microstructure, crack and porosity elimination, phase composition and hardness of graded coatings were investigated by means of optical microscope, microhardness tester, SEM, EDS and XRD. The results show that in the Mo-Ni composite alloy gradient coating, because Mo is easily oxidized to MoO_3 under the action of laser, MoO_3 is easily volatilized by heat and can not escape in the molten pool in time. Therefore, Cracks and pores began to appear in the layer, and the average microhardness was 287.29. In the Mo-Ni-ZrO2 gradient coating, the addition of ZrO2 significantly reduced the cracks and pores in the 50wt% Mo gradient layer. The main phase is MoNi and strengthening phase Mo1.24Ni0.76, Ni3Zr, and a small amount of MoO3, the average microhardness is 477; ZrO2 has a good effect of eliminating the defects of the cracks on the Mo-Ni high-temperature composite alloy gradient coating and the enhanced gradient coating Layer hardness effect.