Research On Hot Deformation Behaviors Of The New Spray Formed Nickel-superalloy

In order to improve the performance and cost savings, alloy composition was optimized by using computer simulation technology, and use the technology of Spray-forming to prepare the powder superalloy which used by the third generation of aircraft engine turbine disc. Heat treatment and hot deformation behavior of Spray formed powder superalloy are studied in this thesis. By system analysis microstructure evolution during heat treatment and hot deformation with OM, SEM. The main results follows:1、According to the thermodynamic software calculations and the theory of controlling phase stability by the d electronic orbital theory to design the composition of the third generation of aircraft engine turbine disc superalloy, the collocation of alloy elements is:Co(15-25%)、Cr(10-15%)、the total amount of Mo and W not less than5%and with more W; the total amount of Ti and Al is about6-10%and Ti/Al=0.9-1.1, Nb(1-2%), Nb/Ta=0.8-1.2.2、The density of the deposit produced by nitrogen spray forming can reaches about99%, pores could be enclosed by HIP and near iso-thermal forging process. The average grain size of the equiaxed grains in the interior of the deposit is about20-40μm, while the grains near the surface of the deposit are finer with average grain size about13um; the primary y’phase which has diameters about0.3-0.5μm possesses irregular block feature.3、The deformation behavior was studied in the different deformation temperatures (1020-1150℃) and different strain rates (0.0003-1.0s-1). The analysis stress-strain curve of hot deformation show that there are four phases:work-hardening, dynamic recovery, dynamic recrystallization and stable strain stage, temperature and strain rate all affect the flow stress. The constitutive equation is established with the Sinh model and draw the hot working figure all by the stress and strain data. Finally the isothermal forging process parameter is:1150℃,10-1S-1.4、The dissolve quantity of primary γ’ were rise with the increasing solution temperature, the precipitation of second γ’increased and mostly from block to a nearly spherical, relatively uniform size. Due to the pinning effect of the crystallization of carbide, the grains is not obviously grew up, show its strong stability. After the aging treatment, the second γ’ grew up obviously than the solution treatment, performance on the mechanical properties is the micro-hardness is increased.