Exploration Of The New High-performance Turbine Disk Alloy Gh742

GH742 alloy is studied comprehensively in this paper from its smelting process tofinal mechanical properties ,and the main aspects include the research of its component,the microstructure of its ingot and forging, the incipient melt temperature, the homo-genization processing of the ingot, the ductility of the ingot and forging, the homo-genization effect on the ductility of the ingot, the mechanism of the way to improve itsductility, the recrystallization rule after deformation ,the final mechanical properties ofthe alloy and so on.It can be obtained GH742 alloy which crossponds with some criterions by VIM+VAR. The dendritic segregation exists in GH742 ingot with the biggest segregationcoefficient 1.714 of Nb. The incipient temperature of ingot is between 1180℃～1200℃,and its reasonable homogenization processing is 1160℃×16h.The soluble temperatureof theγ′phase is about 1100℃,and the coarseγ′phase can be obtained throughcooling slowly during theγ′phase precipitating temperature range.The result of Gleeble test shows that homogenization can improve the ductility of theingot to some extent ,and the coarseγ′phase obtained by cooling slowly can improvethe ductility of the ingot, which mean that the ingot can deform uniformly in widertemperature range and in bigger deformation scale. From the recrystallization degreeafter deformation and the size of grains after solution, it can be tested the coarseγ′phase not only makes the recrystallization temperature rise, but also baffles the grainboundary siding.GH742 forging has the excellent ductility with the largest deformationabout 70% between 1000℃～1100℃.The quicker deformation rate can accelerate therecrystallization, and the optimum grain size can be obtained when the deformationtemperature is 1100℃with the deformation scale of 70% and deformation rate of 1s^-1.The two heat-treatments are compared in this paper, they are (1) 1080℃×8h,Ac+780℃×16h,Ac,(2)1100℃×8h, Ac+850℃×6h, Ac+780℃13h, Ac,respectively.Theresults show that the alloy after heat-treatment(1) has the finer grain ,the coarserγ′phase and the larger quantity ofγ′phase .All of those lead to the strength of the alloyin the processing of heat-treatment(1) is superior to that in heat-treatment(2) at roomtemperature, while the alloy in the processing of heat-treatment (2) has the longerrapture life at 750℃,but it is opposite at 650℃in the processing of heat-treatment(1).Furtherly, the creep and the tensile test show that the alloy in the processing ofheat-treatment(2) has better mechanic performance at high temperature, and in theprocessing of heat-treatment(1) has the better strength at lower temperature.