Microstructure And Tribological Properties Of Ti-based Rare Earth Laser Cladding Layers On Ti811 Surface

Ti811 titanium alloy is widely utilized in aerospace,petrochemical,marine and other national key industrial fields due to its high specific strength,excellent corrosion resistance and oxidation resistance.Laser cladding is the main technology for structural repair and surface modification of titanium alloy.The addition of an appropriate amount of rare earth elements in the laser cladding materials can effectively suppress the generation of defects in the cladding layers such as cracks and pores.In this paper,mixed powders of TC4,Ni45 and CeO₂ were used as cladding materials.The coaxial powder feeding technology and the multi-pass laser cladding technology were used to prepare titanium-base rare earth laser cladding layers on the surface of Ti811 titanium alloy of high-pressure compressor rotor blade of civil aviation turbofan engine.The effects of laser powers and CeO₂ contents on the forming quality,microstructure,microhardness and friction and wear properties of the cladding layers were studied.The optimal laser power parameters and the optimal CeO₂ content were determined.It provides experimental reference and theoretical support for the domestic repair of high-pressure compressor rotor blades and the improvement of friction and wear properties of titanium alloy.It has certain value for engineering application.The main research contents are as follows:?1?The effects of three laser powers of 700 W,900 W and 1100 W on the cracks,pores and other defects of the cladding layers were studied respectively.Additionally the microhardness and friction and wear properties of the cladding layers at three mentioned laser powers were studied.The laser cladding layers prepared by the 75 wt.%TC4+25 wt.%Ni45mixed powder presented less defects such as pores and cracks as the laser power increases.The cladding layers at 900 W laser power displayed the optimum performance with a microhardness of 610 HV_0.2 and a friction coefficient of 0.341.Furthermore,its wear mechanism was dominated by abrasive wear.?2?The effects of 1wt.%,2wt.%,3wt.%and 4wt.%of CeO₂ contents on the forming quality and properties of the cladding layers in TC4+Ni45 cladding powders were analyzed.The optimum CeO₂ content in the cladding material was 3 wt.%,and the surface cracks of the cladding layers were eliminated.The addition of CeO₂ refined the structure of the cladding layers and contributed to fine-grained strengthening.Moreover,it increased the absorption rate of the material to the laser,so that the dilution of the soft substrate to the cladding layers was increased.Thus the microhardness and friction and wear properties of the layers increased firstly and then decreased with the increase of CeO₂ content.?3?The effects of the content of CeO₂ on the phases composition and microstructure of the laser cladding layers were clarified.The addition of CeO₂ in the TC4+Ni45 cladding materials resulted in the formation of rare earth oxide Ce₂O₃ and ceramic reinforcing phases TiC and TiB₂,intermetallic compound Ti₂Ni and matrix?-Ti in the cladding layers.By calculating the planar disregistries between the formed phases,Ce₂O₃ can be used as the heterogeneous nucleation point of TiC and TiB₂.The addition of CeO₂ not only improved the precipitation rate of the cladding phases,but also refined the cladding microstructures.