Microstructure And Properties Of Laser Clad K465 Nickel-Based Alloy Repair Layer

In this paper,aiming at the problem of defects and damages of K465 nickel-based superalloys during manufacturing and repaired rapidly,single-layer single-channel repair experiments,single-layer multi-channel repair experiments and multi-layer single-channel repair experiments are used with nickel-based powder by laser cladding repair technology.The best combination of parameters for laser cladding to repair K465 was screened and applied to the trench repair of the K465 substrate to simulate damage,achieving a high-quality repair.Further implementing a two-stage aging treatment on the repair layer to improve the performance of the laser cladding K465 repair layer,which focuses on tensile properties.In order to improve the high temperature hot corrosion resistance of the repair samples,different contents of rare earth Y₂O₃ were added to the repair powder to explore the effect of the rare earth content on the high temperature hot corrosion resistance.The results show that the optimal parameters for laser cladding repair K465 are:P(laser power)=2400W,V(scan rate)=6mm/s,V₀(powder supply speed)=12g/min,overlap rate43.3%,and?Z(layer thickness)=1mm.With the growing of P,the trunk and crystal arms of the dendrites become coarse,and the distance between the secondary dendrite arms also increases significantly.As V increases,the dendrite structure becomes finer.After simulating the repair of K465 substrate,the overall deformation is not large.However,a large angular displacement on the right of the cladding end direction happens.When the length is 20 mm,it is approximately 1.73°,and the thickness is retracted 0.2mm approximately inward.The repair zone shows typical epitaxial growth of columnar dendrites,and?and?'phases exist in the repair layer.The average microhardness of the repair layer is297.3HV which slightly lower than the substrate(310.4HV);the abrasion loss of the repair layer is slightly higher than the substrate,and the friction coefficient is reduced by about 15.7%compared with the substrate;the tensile strength of the repair layer has reached the substrate93.6%of the material.After the two-stage aging treatment,the?'phases in the repair layer begin to precipitate and grow,and as the aging temperature increases,the?'phases grow more obvious,and the?'phases spacing also became larger;after the aging treatment,the hardness of the repaired area increases significantly.the hardness of the air-cooled repair specimen reaches the maximum360.5HV after aging at 840?×12h+780?×8h;the abrasion loss of the repair layer reduces,and the wear resistance reaches 1.52 times than before.When aging at 860?,the carbides precipitated in a necklace shape.At 880?,the carbides changed from discontinuous particles to continuous film formation.At this temperature,the tensile strength of the aging sample become the maximum,which is about 12.1%higher than that before the aging treatment.With the growing of the content of rare earth Y₂O₃ in the repair layer,the thermal corrosion gain decreases.When the content is 1.5%,the corrosion weight increase instead.Among them,the Y2 repair layer(Y₂O₃ content is 1.0%)has the best resistance to high temperature hot corrosion.With the increasing content of rare earth Y₂O₃ in the repair layer,the high-temperature corrosion resistance of the repair layer decreases gradually.The reason is that the harmful Ni₁₇Y₂ phase appears in the repair layer,and the existence of this phase adversely affects the high-temperature corrosion resistance of the repair layer.