Research On The Structure And Properties Of Laser Cladding Coating On Ti811 Surface

Ti811 titanium alloy has a promising application prospect as the indispensable part of civil aviation engine compressor blades.Ti811 titanium alloy can be used in high temperature environment for a long time.Besides good weldability,high temperature properties,it also has high Young Modulus,low density and excellent vibration damping properties.However,the wide application of Ti811 titanium alloy is limited owing to its low hardness and poor wear properties.To improve microhardness and tribological properties of the Ti811 titanium alloy,microstructure,microhardness and tribological properties of the coatings were investigated systematically,providing scientific evidence and theoretical supporting for the laser cladding process optimization and microstructure controlling of Ti811 titanium alloy.The main research contents are as follows:(1)The optimum laser parameters in this experiment were:P=900 W,v=400 mm/min,D=3.0 mm,overlap ratio,=50%.The dilution rate of single coating,maximum penetration depth of multi-pass overlapping coating and cross-sectional cladding area were directly proportional to laser powers and inversely proportional to laser scanning speeds.(2)Phases of the coatings were identical under different laser powers and scanning speeds which mainly consist of matrix a-Ti,ceramic reinforced phases TiC,TiB2 and intermetallic compound Ti2Ni.The misfit between(0001)surface of TiBz and(111)surface of TiC was only 1.057%.Long rod shaped TiB2 can be the most effective heterogeneous nucleation core of TiC phase to form a TiB2-TiC composite phase structure.Due to the combined effects of dispersion strengthening,solution strengthening and fine grain strengthening,microhardness of the coating was 617HV0.5,which was 1.62 times than that of the Ti811 substrate.(3)CeO2 had little effect on phase composition of the coatings."Herringbone"cracks in the multi-pass overlapping coatings can be eliminated by adding 2 wt.%CeO2.Adding appropriate amount of CeO2 can improve the surface quality of the coating.(4)Mechanical properties can be significantly improved by adding a small amount of CeO2,but adding excessive CeO2 will reduce the refining effect.The precipitation of TiC phase in the coating was inhibited and the number of reinforcing phases was reduced.Compared with the Ti811 substrate,the microhardness and wear resistance of the coatings with 2wt.%CeO2 increased by 2.08 and 4.56 times,respectively.The wear mechanisms were mainly slight adhesion wear and abrasive wear.