Microstructure And Properties Of Laser Cladding NI/CRXSY Composite Coating On Titanium Alloy Surface

In order to improve the surface properties of titanium alloy,Ni-based wear resistant and Ni-based wear-resistant and self-lubricating composite coatings were prepared on the surface of TC4 alloy by using fiber laser,and using Ni20Cr,Ni20Cr+MoS2,Ni20Cr/Cr3C2 and Ni20Cr/Cr3C2 +MOS2 alloy powders as raw materials.The macro morphology and microstructure of coating were examined by OM,SEM,XRD and EDS and et,microhardness tester,friction wear testing machine and electrochemical workstation are used to explore the surface properties of the coatings.At last,the phase composition of the coating and the transformation process of the molten pool are analyzed by the thermodynamic software JMatPro.Ni20Cr coating is mainly composed of γ-Ni and uniform distribution of CrB,the crystallization process is:liquid → liquid +γ-Ni → liquid + γ-Ni + CrB→γ-Ni + CrB.Ni20Cr + MoS2 coating is mainly composed of γ-Ni and CrxSy,Ti2S,Mo2B and Cr2B,CrxSy is a variety of sulfide mixed tissues of Cr and spherulously distributed in the coating.The two borides of Mo2B and Cr2B are distributed around CrxSy,The hardness of Ni20Cr coating,Ni20Cr+MoS2 coating and TC4 substrate were 1045 HV0.3,960 HV0.3 and 290 HV0.3 respectively,the friction coefficient between 0.42～0.45,0.36～0.39 and 0.50～0.55,weight losses were 12.2 mg,17.3 mg and 26.1 mg,the cladding layer significantly improves the surface hardness and wear resistance of TC4 alloy.The self-corrosion potential of TC4 alloy,Ni20Cr+MoS2 coating and Ni20Cr coating increased sequentially,while the self-corrosion current density decreased.The cladding layer significantly improved the corrosion resistance of TC4 alloy.Ni20Cr/Cr3C2 coating is mainly composed of γ-Ni、Cr7C3 and TiC.The crystallization process is:liquid→liquid +TiC→liquid +TiC+ Cr7C3→liquid +TiC+Cr7C3+ γ-Ni → TiC+ Cr7C3+ γ-Ni.Ni20Cr/Cr3C2 +MoS2 coating is mainly composed of γ-Ni,Cr7C3,CrxSy and little TiC.The hardness of Ni20Cr/Cr3C2 coating,Ni20Cr/Cr3C2+MoS2 coating and TC4 substrate is 1193 HV0.3,1094 HV0.3 and 290 HV0.3 respectively,and the friction coefficient is between 0.40～0.42,0.31～0.33 and 0.50～0.55,The wear loss weight is 5.9 mg,10.1mg and 26.1 mg,the wear resistance of the coating is improved.After the addition of MoS2,the wear of the coating increased because the hardness of the Ni20Cr/Cr3C2+MoS2 coating was lower than the NiCr/Cr3C2 coating,but on the other hand,the CrxSy in the Ni20Cr/Cr3C2 +MoS2 coating forms a layer of lubricating film on the contact surface,which reduces the friction coefficient of the coating and improves the lubrication performance.The corrosion resistance of the cladding layer is also enhanced compared with the TC4 alloy.