铌对镍基合金激光熔敷层组织和显微硬度的影响

Effects of Niobium Element on Microstructure and Microhardness of Ni-based Alloy Laser Cladding Coating

采用激光熔敷技术在42CrMo钢基体上制备了不同铌含量的镍基合金熔敷层,研究了铌含量对熔敷层显微组织、物相组成、显微硬度的影响。结果表明:在镍基合金熔敷层与基体结合处、熔敷层中部、熔敷层表面的组织分别为平面晶、树枝晶、粒状等轴晶组织;随着铌含量的增加,熔敷层组织逐渐由γ-Ni奥氏体、CrB、M7C3和M23C6以及Ni31Si12相转变为由γ-Ni枝晶、枝晶间共晶、NbC小颗粒和少量CrBC4等;当铌质量分数达到10%时,组织明显细化;熔敷层的显微硬度随着铌含量的增加而增大,当铌质量分数达到10%时,显微硬度最高,达到约550HV0.2,约为不含铌镍基合金熔敷层的两倍。

Several Ni-based alloy cladding coatings with different Nb element contents were successfully fabricated on the substrate of 42 CrMo steel by laser cladding technology.The effects of Nb contents on microstructure,phase composition and microhardness of the cladding coatings were investigated.The results show that the microstructure of the interface between the cladding coatings and substrate,the central part of the cladding coating and the surface of the coating were successively planar crystal,dendrite,granular isometric grains;with the increase of Nb element content,the microstructure of the cladding coatings was mainly composed ofγ-Ni dendrites,interdendritic eutectics,dispersed NbC particles and a few CrBC4 type chromium borides instead ofγ-Ni phase,CrB type chromium borides,M7 C and M23C6 type carbides and Ni31Si12 type silicide.When Nb element content was10wt%,the microstructure refinement was particularly significant.In addition,the microhardness of the cladding coatings gradually increased with the increase of Nb element content,When Nb element content reached 10wt%,the microhardness of the cladding coating was maximum(about 550HV0.2),it was twice that of the Ni-based alloy cladding coating without Nb element.