| Titanium alloy has properties of high specific strength,biocompatibility,good corrosion resistance and heat resistance,and it's extensively applied in marine engineering,aerospace,biological medical treatment fields,etc.However,the friction and wear properties of titanium alloy are poor,which limits its wide application as high-temperature tribological moving components,such as intermediate brake,forging titanium fans,compressor plates and blades,etc.In order to improve the friction properties of Ti6A14V alloy,high temperature self-lubricating wear resistant composite coatings were prepared on the surface of Titanium alloy by laser cladding technology.At present,the majority of the single lubricants have good lubrication effects in a narrow temperature range,while there is few studies focus on the self-lubrication wear resistance coatings in a wide temperature range.The reason is that some solid lubricants are invalid at high temperature,and the comprehensive application of various solid lubricants is a choice to solve this problem.Ni60-16.8%TiC-23.2%WS2(N1 coating)and Ni60-19.6%TiC-20.4%WS2(N2 coating)alloy powders have been chosen as raw materials and high temperature anti-wear self-lubricating composite coatings has been synthesized on Ti6A14V alloy by laser cladding.The microstructure and phase compositions have been analyzed by scanning electron microscope(SEM),energy dispersive spectroscopy(EDS),X-ray diffraction(XRD).The microhardness of the composite coatings and substrate has been measured by digital microhardnes tester,and the hardness strengthening mechanisms of the composite coatings was analyzed.The wear rates and friction coefficients of the substrate,N1 and N2 coatings at 20?300?600?800? have been measured by ball-disc high temperature friction and wear tester,probe-type material surface wear mark measuring instrument,respectively,and the corresponding wear mechanisms of the composite coatings were analyzed systematically.The wear mechanisms of the composite coatings at different test temperatures have been studied in depth and systematically by means of SEM?EDS and XRD.The results showed that the N1 and N2 coatings have good bonding with the substrate,and there are no obvious defects in the coatings.N1 and N2 coatings are mainly composed of three types of phases:solid lubrication phases TiS and NiS,solid solution(Cr,Ni),hard phases TiC,Cr7C3 and(Ti,W)C1-x.The average microhardness of N1 coating and N2 coating are 737.92 HV0.5 and 839.87 HV0.5,respectively.The microhardness of the coatings are obviously improved compared with that of the substrate(350 HV0.5),which is mainly attributed to the dispersion strengthening effect of in situ synthesized hard carbides TiC,(Ti,W)C1-x and Cr7C3 particles during the lase cladding.The friction coefficients and wear rates of N1 and N2 coatings are lower than those of Ti6A14V alloy substrate at 20 to 800?,showing excellent properties of high temperature self-lubricating wear resistance.The friction coefficients of the substrate at 20 to 800? are 0.53,0.50,0.45 and 0.43,respectively,and wear rates at 20 to 800?are 5.4 ×10-4,2.64×10-4,1.98×10-4,1.80×10-4 mm3/Nm,respectively.The friction coefficients of N1 coating at 20 to 800? are 0.44,0.39,0.38 and 0.32,respectively,and wear rates of at 20 to 800? are 1.36×10-4,5.94×10-5,3.74×10-5,2.92×10-5 mm3/Nm,respectively.The friction coefficients of N2 coating at 20 to 800? are 0.49,0.43,0.44 and 0.40,respectively,and wear rates of the N2 coating at 20 to 800?are 1.1×10-4,4.8×10-5,4.5×10-5,2.3×10-5mm3/Nm,respectively.The main wear mechanisms of N1 coating at 800? are oxidation wear and slight adhesion wear,the main wear mechanisms of N2 coating at 800? are oxidation wear and slight three-body abrasive wear. |
PDF Full Text Request