Laser Deposition Repair Process Research Of GH4169 Alloy

GH4169 high temperature alloy has been widely used in the fields of aerospace, nuclear power and energy industry because of its excellent mechanical properties. In this paper, the laser deposition repair process of penetrating crack and groove wear is studied based on the requirement of rapid repair of GH4169 alloy parts after damage. The microstructure, stress reduction and mechanical properties of GH4169 alloy were studied by the laser deposition state, preheating state and various heat treated state. The main results of the study are as follows:After optimizing the process parameters of laser deposition repair of GH4169 alloy by orthogonal test, the samples with no porosity and poor fusion defects were obtained. The tissue of the repaired area of the deposited state repair sample is the columnar dendrite which runs through the multilayer epitaxial growth. There is a small angle between the dendrite, in the dendrites of the precipitation of white dendritic Laves phase, tensile properties at room temperature to reach the casting standard.In order to improve the performance of GH4169 alloy deposited samples, the method of preheating assisted laser deposition was used to reveal the influence of preheating process on the microstructure and mechanical properties. The results show that the dendrite structure of the repaired sample is not changed when the preheat to 300?. The precipitation phase of Laves was granular and the residual stress was reduced by more than 11.7%. The tensile strength are basically consistent with the sample without preheating, the elongation is increased to Q/3B 548-1996(high strength) forging standard level.Reveal the changes of the microstructure and properties of the repaired samples with different heat treatment processes. After the aging treatment with different time to the samples,the Laves phase was dissolved in a small amount, and the strength reached the standard, and the plasticity decreased slightly. After solution treatment, the Laves phase was partially dissolved, and a large number of needle ? phases were precipitated around it, strength reachedthe forging standard, the elongation increased by 21%. After homogenization treatment, the Laves phase is basically dissolved, and the ? phase is precipitated in grain boundary and grain,strength close to the forging standard, elongation more than 27.1% forging standard. Tests show that the appropriate heat treatment can effectively improve the strength and plasticity of GH4169 alloy deposited samples.In view of the problems of easy deformation and complicated loading in the whole heat treatment of large thin wall workpiece, the method of local heat treatment based on induction heating is proposed. After local aging treatment of GH4169 alloy, the dendrite microstructure was not changed, and the Laves phase was partly dissolved. The residual stress is reduced by more than 33.5%, and the strength is above 86.8% of the forging level. The test shows that the local induction heat treatment can reduce the repair stress of large thin wall workpiece.