Study On The Hot Deformation Behavior And Microstruc-ture-properties Of GH3536 Superalloy Prepared Based On SLM Process

GH3536 superalloy is a typical solid solution strengthened nickel-based superalloy,it has excellent high temperature performance,oxidation resistance and thermal stability,can be used for a long time below 900°C,can work for a short time at 1080°C,and is often used in the manufacture of nuclear reactor heat exchangers,aero-engine combustion chambers and other high-temperature components.Selective laser melting（SLM）is an efficient,pre-cise and low-cost metal additive manufacturing technology,which has been widely used in aerospace and other fields with excellent technical characteristics.In this paper,GH3536superalloy prepared by selective laser melting technology is used as the basic material for research.The alloying degree of the metal is relatively high,the deformation resistance is large,the geometry of the prepared aviation parts is complex,and the deformation is ex-tremely uneven.Hot deformation behavior and microstructure evolution may occur under the action of high temperature and stress during the working process of alloy parts,which will greatly affect the performance of the alloy.Therefore,studying the hot deformation be-havior and microstructure evolution law of GH3536 nickel-based superalloy has guiding significance for improving the mechanical properties and service performance of aviation products.In this paper,the GH3536 superalloy prepared by selective laser melting technology was subjected to hot isostatic pressing and hot isostatic pressing+heat treatment,respec-tively,to obtain the GH3536 superalloy in the deposited state,hot isostatic pressing（HIP）and hot isostatic pressing+heat treatment（HIP+HT）.Based on Gleeble-3800 single-pass hot compression experiment,GH3536 superalloys in these three states were subjected to hot compression experiments under the conditions of a deformation temperature of 900°C,950°C,1000°C,1050°C and strain rate of 0.01 s^-1,0.1 s^-1,1s^-1 and 10 s^-1.Using the rheo-logical stress curves and data obtained experimentally,the Arrhenius constitutive model of the GH3536 superalloy in three states was established,and the accuracy of the constitutive model was verified.The effects of deformation temperature,strain rate,and stress on the hot deformation process of GH3536 superalloy were analyzed.The microstructure characteriza-tion was carried out by OM,SEM,TEM,EBSD and the effects of deformation temperature and strain rate on the macromorphology,microstructure evolution,and dynamic recrystalli-zation mechanisms of the three superalloys after hot deformation were analyzed.It is found that the stress-strain curve of GH3536 superalloy is mainly divided into three stages,name-ly the work hardening stage,the dynamic softening stage（dynamic recovery/dynamic re-crystallization）,and the steady-state rheological stage.The rheological stress decreases with increasing temperature and increases with an increase in strain rate.The established consti-tutive model has high accuracy and can predict the rheological stress of GH3536 superalloy under different deformation conditions.The original structure of the sedimentary GH3536 superalloy is a"fish scale"molten pool structure,which contains microcracks and pores inside,and the sample is seriously cracked at the strain rate of 0.01～1 s^-1.The original structure of GH3536 in HIP state was uniformly equiaxed crystals,the molten pool structure disappeared,the cracks were closed,and the overall mechanical properties were improved,but M₆C or M₂₃C₆ type precipitates appeared.The tissue of GH3536 in the HIP+HT state is more refined,the partial analysis extract is dissolved,and the microstructure and performance of GH3536 in this state are op-timal.The GH3536 superalloy,in all three states,undergoes dynamic recrystallization or dynamic recovery during the hot deformation process.Higher temperatures and lower strain rates favor dynamic recrystallization.The dynamic recrystallization mechanism was mainly DDRX,and CDRX was used as the auxiliary nucleation mechanism.Both precipitates and twin boundaries favor the nucleation of recrystallized grains.The deformation and recrys-tallization of the alloy are inhomogeneous,especially at high strain rates,and the degree of recrystallization in the center of the specimen is high.