Preparation And Properties Of High Temperature Modified Coatings On TC4 Titanium Alloy

TC4 titanium alloy has excellent properties such as low density,high strength and corrosion resistance,and is mainly used in aircraft landing gear and aeroengine fan,wheel and other parts.Load-bearing parts made of TC4 titanium alloy are mostly used under high temperature load-bearing conditions,but its shortcomings of low hardness and poor creep resistance limit its application range.In this paper,Ni fundal-ceramic composite coating was prepared on the surface of TC4 titanium alloy by laser cladding technology with GH4169 nickel-based superalloy powder as the base powder and Nb C,Hf C,Ta C and Zr C as the reinforcing phase.The effect of different proportions of carbide powder and base powder on the microstructure of TC4 surface coating and the enhancement of the anti-plastic deformation ability of the cladding coating were investigated.Firstly,four kinds of cladding coating materials of different proportions were designed,and the laser cladding coating was prepared on the surface of TC4 with appropriate technological parameters.The macroscopic morphology and microstructure of the cladding coating were compared and analyzed by electron microscope,SEM scanning electron microscope,XRD diffractometer and other instruments,and the changes in hardness of the coating were measured by microhardness tester.The results showed that:The addition of ceramic strengthening phase refines the microstructure of the coating and improves the hardness.When the addition amount is 15%,the hardness is the highest,which is 2.54 times that of the substrate.Secondly,the TC4 specimen without coating and the specimen with 0% and 15%ceramic powder added by laser cladding nickel-based alloy coating were subjected to high temperature compression experiments with Gleeble-3500 thermal simulator,and the test data and microstructure of the specimen after the test were analyzed.The results show that:The variation trend of the true stress-strain curves of the three specimens is the same.The phase of TC4 changes after compression deformation,and the dendrite structure in the coating is broken and equiaxed.Finally,a finite element analysis model of specimens under high temperature compression was established to analyze the changes and distributions of stress and strain inside specimens during the compression process.The curves of stress and strain changes along the path were drawn with the central axis of specimens as the path.The results showed that: The coating enhances the plastic deformation resistance of the TC4 matrix at high temperature,but the stress mutation occurs in the bonding zone between the coating and the substrate.The numerical simulation data are converted into true stress-strain curves,which are in good agreement with the experimental results.