Study On Hot Deformation Behavior And Hightemperature Oxidation Properties Of High Al Equiaxed Ni₃Al Alloy

With the continuous updating and iteration of fighter jets,the requirements for the use of aero-engines are getting higher and higher,so the development of materials that meet the requirements of today’s aero-engines has become a key issue for the country to solve.As an important part of aero-engine,the performance of combustion chamber directly affects the comprehensive performance of aero-engine.In this paper,Ni₃Al-based superalloys are studied based on the requirements of combustion chamber materials.The purpose of increasing the content of Al element through composition design is to improve the hot workability and high-temperature oxidation resistance of the alloy under the premise of ensuring high-temperature performance.In the smelting process,the advanced smelting equipment at home and abroad is adopted to make the H,O,N contents in the alloy reach 0.00004 wt%,0.0013 wt%,0.0002 wt%respectively,which provides a strong guarantee for the comprehensive properties of the alloy.The thermal deformation process is simulated by deform-3D finite element simulation software,and the simulation results are compared with the experimental results,which proves the accuracy of the thermal deformation process simulation and provides reliable theoretical parameters for isothermal compression experiments.The hot deformation behavior of equiaxed Ni₃Al alloy with high Al content was investigated by isothermal compression experiments.The Arrhenius-type constitutive equation based on peak stress and the strain-compensated constitutive equation based on the Arrhenius-type constitutive equation for predicting flow stress was established.The stress values of the equiaxed Ni₃Al alloy with high Al content under different deformation conditions provide higher precision prediction parameter values.The DMM theoretical hot working diagram of the high Al content equiaxed Ni₃Al alloy is established,and the parameter ranges of the safe machining area and the instability area of the high Al content equiaxed Ni₃Al alloy under different strain conditions are given.The stress-strain curves and hot working diagrams of the high Al-content equiaxed Ni₃Al alloy have typical DRX characteristics,and the DRX mechanism is identified as a continuous dynamic recrystallization mechanism by TEM characterization.By establishing the internal relationship between the true stress-strain curve,the hot working diagram,the microstructure,a reliable theoretical basis is provided for the actual hot working process of the high Al content equiaxed Ni₃Al alloy.Equiaxed Ni₃Al alloy with high Al content is rated as complete anti-oxidation grade according to the"Standard for Evaluation of High-Temperature Oxidation Resistance of Superalloys,Protective Coatings,etc."after being oxidized at 950℃and 1050℃for 100 hours in atmospheric environment,and it belongs to secondary oxidation resistance at 1150℃level.The oxidation rates of 100h oxidation at 950℃,1050℃and 1150℃are 0.3947 mg/cm²,0.7432 mg/cm² and 1.9811 mg/cm²,respectively.The high-temperature oxidation kinetic curves at the three temperatures are all in line with the high-temperature oxidation parabolic law;The high-temperature oxide film growth rate K_p values were 0.0015 mg²cm^-4/h,0.0063mg²cm^-4/h,and 0.0502 mg²cm^-4/h,respectively.The main phase composition of the oxidized surface is Ni₃Al phase,Al₂O₃phase,Ni Al₂O₄ phase.Compared with IC6 alloy with high W and Mo content,the equiaxed Ni₃Al alloy with high Al content has obvious improvement in high-temperature oxidation resistance.