High-temperature Oxidation And Hot Corrosion Behavior Of Plasma Sprayed CoNiCrAlY Bond Coat By Laser Shock Processing

Turbine engines are rapidly developing in the aerospace field,and high-temperature oxidation and hot corrosion protection of the hot-end components of turbine engines is important.Thermal barrier coatings?TBCs?can improve the high-temperature oxidation resistance and hot corrosion resistance of hot-end parts.The surface strengthening technology can refine the grain of the bond coat to promote the selective oxidation of Al,Cr and other elements,and quickly generate dense oxidation,thus further improve the oxidation resistance and corrosion resistance of thermal barrier coating.In this paper,the CoNiCrAlY bond coat was prepared by atmospheric plasma spraying?APS?on the base of superalloy GH4169.The CoNiCrAlY bond coat was modified by laser shock processing?LSP?.The microstructure and mechanical properties of the bond coat after LSP were analyzed.And the high-temperature oxidation resistance and hot corrosion behavior of the bond coat before and after LSP were studied,and the effect of LSP on the resistance to high temperature oxidation and heat resistance was analyzed.The main researches were as follows:?1?The surface modification of plasma spraying CoNiCrAl Y bond coat was carried out by LSP.The laser shock parameters were optimized and the optimal laser energy was selected as 15 J.The surface pits are more obvious and smooth without dents and other defects with 15 J.?2?The microstructure and mechanical properties of the plasma sprayed CoNiCrAlY bond coat were effectively controlled by LSP.There are a large number of unmelted and semi-molten particles in the plasma sprayed CoNiCrAlY bond coat,showed a typical stacked layered structure.The holes on the surface of the bond coat after the LSP were significantly reduced,and a plastic deformation zone with a thickness of 8³0?m was produced.The grain refinement of?/??phase was evenly distributed in the plastic deformation zone.The maximum microhardness of the bond coat reached 494 HV,increased 75.8%.And the maximum surface residual stress was-385MPa,increased 286.9%.?3?The constant temperature oxidation experiment was carried out on the bond coat before and after LSP with different impact at a constant temperature of 1000?.After the oxidation of 100 h,the surface oxidation film of the sprayed state and the polished state bond coat was mainly?Ni,Co??Cr,Al?₂O₄.And TGO was relatively loose.After 1 time impact,the surface oxidation film of the bond coat was mainly Al₂O₃ and NiCr₂O₄.And TGO was dense and has a single Al₂O₃ structure.When the number of laser shocks were increased to three times,the oxide film was mainly composed of Al₂O₃ and NiAl₂O₄.The TGO exhibited a double layer structure and the oxide film did not fall off.The grain of the bond coat with LSP has provided short circuit channel for Al ion diffusion.Al₂O₃ layer was formed in a short time,which can improve the high temperature oxidation resistance of the bond coat.?4?The hot corrosion test of the bond coat before and after LSP was carried out at different temperatures?800?,900??.After 10h,the main surface oxide of the polished bond coat was loose Cr₂O₃.After LSP,the surface oxide of the bond coat was Al₂O₃,which performed excellent thermal corrosion resistance at 800?.The decrease of Al content in the bond coat can not fully provide the Al elements needed to form Al₂O₃ at 900?.The formation of dense Cr₂O₃ on the surface hinders the further corrosion of the bond coat and enhances the corrosion resistance of the bond coat.