Nb_2O_5对镍基合金激光熔覆层组织的影响

Effect of Nb_2O_5 on the Microstructure and Properties of Laser Cladding Layers of Ni-Based Alloy

为了在钢材表面制备出质量良好、组织细化的镍基合金激光熔覆层,采用激光熔覆技术,在A3钢表面进行了镍基合金粉末添加Nb2O5的熔覆试验.通过对激光熔覆工艺参数及Nb2O5含量的优选得到了质量良好的熔覆层.使用金相显微镜、扫描电镜、电子能谱和X射线衍射仪对熔覆层进行了显微组织和物相分析,并测试了熔覆层显微硬度及摩擦性能.结果表明,当Nb2O5含量为15%,激光功率1.4 kW,扫描速度2 mm/s时,可以获得无裂纹、无气孔且与基底呈冶金结合的质量良好的熔覆层.Nb2O5的加入既提高了镍基合金熔覆层中的强化相比例,又细化熔覆层的组织,抑制粗大针状脆性硬质相的形成,降低熔覆层的裂纹敏感性.Nb2O5/Ni60激光熔覆层的硬度虽然降低,但耐磨性比纯Ni60提高约一倍.

In order to achieve a perfect and organization refinement cladding layers of Ni-based alloy on the steel products surface,by laser cladding,the experiments of Ni-based composite alloy powder doped with Nb2O5 were carried out on A3 steel substrate.Various laser processing parameters and different Nb2O5 content were chosen to obtain a perfect clad layer.The microstructural and metallographic analyses by a scanning electron microscopy,energy-dispersive spectrometer and X-ray diffractometer suggest that a good finish and crack and porosity free surface clad layer was obtained with the Nb2O5 content of 15% at the beam scanning velocity of 2mm/s.The microhardness test of the cross-section of laser-clad layer were also performed.It is shown that the addition of Nb2O5 with a proper content can enlarge the proportion of the reinforcements in the coatings,refine the grain,suppress the formation of big nubbly hard phases,and reduce the cracking susceptibility obviously.The coatings give the low average hardness,but the excellent wear resistance is higher than that of pure Ni60 coatings.