Ti6Al4V合金激光熔覆Ti_(3)SiC_(2)增强Ni60复合涂层组织与摩擦学性能

Microstructure and Tribological Properties of Ti_(3)SiC_(2) Enhanced Ni60 Composite Coatings on Ti6Al4V Alloy by Laser Cladding

为了提高Ti6Al4V合金的耐磨减摩性能,在其表面利用激光熔覆技术制备出两种不同配比的Ti3Si C2/Ni60复合涂层,分别是5%Ti_(3)SiC_(2)+Ni60(N1)和10%Ti_(3)SiC_(2)+Ni60(N2)(均为质量分数),研究了这两种涂层在室温、300和600℃下的微观组织、显微硬度、摩擦学性能表现及相关磨损机理.结果表明:涂层主要由硬质相TiC/TiB/Ti_(x)Ni_(y),γ-Ni固溶体连续相和润滑相Ti_(3)SiC_(2)组成.N1、N2涂层的显微硬度均为基体(350HV_(0.5))的3倍左右,分别为1101.90HV_(0.5)和1037.23HV_(0.5),在室温、300和600℃下的摩擦系数分别为0.39、0.35、0.30和0.41、0.45、0.44,均小于基体的摩擦系数(0.51、0.49、0.47).N1、N2涂层在室温、300和600℃下的磨损率分别为3.07×10^(-5)、1.47×10^(-5)、0.77×10^(-5)mm^(3)/(N·m)和1.45×10^(-5)、0.96×10^(-5)、0.62×10^(-5)mm^(3)/(N·m),均远小于基体[35.96×10^(-5)、25.99×10^(-5)、15.18×10^(-5)mm^(3)/(N·m)].在本文中Ti_(3)SiC_(2)提高了Ti6Al4V合金的耐磨减摩性能,使得N1涂层表现出更好的减摩性能,N2涂层表现出更好的耐磨性能.室温下,磨粒磨损、塑性变形以及轻微的黏着磨损为两种涂层的主要磨损机理;300℃时,塑性变形、氧化磨损和黏着磨损是N1涂层的对应机理,600℃时出现了三体磨粒磨损;在300和600℃时,黏着磨损、氧化磨损及磨粒磨损为N2涂层的主要磨损机理.

Ti6 Al4 V alloy(TC4)has excellent comprehensive mechanical properties,so it is widely used in jet engine pressure disc,pressure boat body,water ship pump body and industrial fuselage fire wall.However,due to the poor oxidation resistance and tribological properties in high temperature environment,its application was greatly limited.Therefore,two kinds of Ti_(3)SiC_(2)/Ni60 composite coatings,i.e.5%Ti_(3)SiC_(2)+Ni60(N1)and 10%Ti_(3)SiC_(2)+Ni60(N2)(weight fraction)were prepared by laser cladding technology on the Ti6 Al4 V alloy to enhance the wear resistance and friction reduction performance.The microstructure,microhardness,tribological performance and the related wear mechanisms of the composite coatings were investigated at room temperature(RT),300 and 600℃by using various characterization methods(scanning electron microscopy,X-ray diffraction,energy dispersive spectrometer).According to the results,the composite coatings were mainly composed of hard phase TiC/TiB/Ti_(x)Ni_(y),γ-Ni solid solution continuous phase and lubricating phase Ti_(3)SiC_(2)at room temperature;however,at high temperature,dense oxide films of TiO2 and SiO2 with certain lubricating effect were produced.In addition,the microhardnesses of N1 and N2 composite coatings were 1101.90 HV_(0.5)and 1037.23 HV_(0.5),respectively,which were about three times that of the substrate(350 HV_(0.5)),due to the effects of dispersion strengthening,solid solution strengthening,fine grain strengthening and the feature of ternary lubricating phase Ti_(3)SiC_(2)with the dual effects of metal and ceramic.The coefficients of friction(COF)of the N1 composite coatings at room temperature,300 and 600℃were 0.39,0.35 and 0.30,while the N2 composite coatings were 0.41,0.45 and 0.44,which both were lower than those of substrate(0.51,0.49,0.47).The wear rates of N1 and N2 composite coatings at room temperature,300 and 600℃were 3.07×10^(-5),1.47×10^(-5),0.77×10^(-5)mm^(3)/(N·m)and1.45×10^(-5),0.96×10^(-5),0.62×10^(-5)mm^(3)/(N·m)respectively,which both were far lower than those of the substrate[35.96×10^(-5),25.99×10^(-5),15.18×10^(-5)mm^(3)/(N·m)].It can be seen that the addition of ternary solid lubricating phase Ti_(3)SiC_(2)improved the wear resistance and friction reduction properties of Ti6Al4 V alloy in this work,rendering N1 composite coating better friction reducing performance and N2 composite coating better wear resistance.At room temperature,the wear of the substrate was mainly caused by abrasive wear,adhesive wear and plastic deformation;while abrasive wear,mild adhesive wear and plastic deformation were the main wear mechanisms of the two composite coatings.In the high temperature wear process,the surface of Ti6Al4V alloy was dominated by oxidation wear,adhesive wear,abrasive wear and mild plastic deformation.At 300℃,three-body abrasive wear,adhesive wear and oxidation wear were the main wear mechanisms of the two composite coatings.At 600℃,the main wear mechanisms were abrasive wear,adhesive wear and oxidation wear,and the plastic deformation of N2 composite coating was relatively severe.