Studies On The Microstructure And Properties Of Additive Manufactured Ni-based Repair Cladding Prepared By Micro-plasma Arc Welding

Micro plasma arc welding?MPAW?is extensively applied in the remanufacturing repair process because of its high energy density and low heat input.Many components which are work in harsh operating environments may fail on account of high temperature oxide,abrasion and corrosion.This paper studied the MPAW repairing technology and optimized the microstructure and properties of Ni-based cladding.This study simulated the welding temperature field of Ni-based repairing cladding which was prepared on thin plate by micro-plasma arc welding.The results show that a composite heat source model compound by plane-gauss model and double-ellipsoid model can accurately reflect the heat input of MPAW.The thermal recycle affected the crystallization of repairing cladding and lead to the columnar grain structure vertically growing from the fusion line,some coarse grain distributing in the cladding center and some needle-like structure distributing in the upper cladding.The studies of microstructure and properties show the cladding is mainly composed by Ni-base solid solution and compounds such as Cr₂B,Cr₇C₃,Cr₂C and Ni₄Si₃,the microharndess of the cladding center is 580HV0.2.To improve the high temperature oxidation resistance and wear resistance,the rare earth oxide Y₂O₃ was addicted in the powder.A series of composite repairing claddings with different amounts of Y₂O₃ were obtained.We studied the influence of Y₂O₃ on the weldability,microstructure,microhardness,oxidation resistance and wear resistance of the Ni-based repairing cladding.The results show that with the increase of the content of Y₂O₃,the cladding width will increases first then decreases,and reaches the maximum when Y₂O₃ content is 1%,while the reinforcement and the contact angle will keep decreasing.The addition of Y₂O₃ make the size of precipitates decrease but the distribution density increase.With the content of the Y₂O₃ increase,microhardness and wear resistance increase first then decrease,and reach the maximum when Y₂O₃ content is 1%.When the content of Y₂O₃?1%,the oxide film growth rate is reduced by the content of Y₂O₃ increase,rare earth oxide Y₂O₃ can delay the oxidation process.Thus,the high temperature oxidation resistance of the cladding is increased.