Research On High-speed Hot Deformation Behaviors And Hot Extrusion Process For IN690Superalloy Tube

IN690was an austenitic nickel-based superalloy with about30%chromiumcontent. It was considered as the new generation steam generator tubes in nuclearpower plants. It was widely used because of the excellent corrosion resistance, andhigh strength, and good metallurgical stability and nice processing characteristics.Thermal-deformation behaviors and high-speed extrusion process for tube of IN690superalloy had been studied by theoretical and experiment method. The main resultsand conclusions are as follows.(1) The solution heat treatment experiment was used to obtain the rules ofcarbide dissolving and grain growth for IN690. The model of grain growth wasestablished and reasonable method of solution heat treatment was found based on thisexperiment. It provides the advantageous preparation for high speed hot compressionexperiments.(2) The true stress-strain curves had been obtained under different deformationparameters through the high speed and hot compression experiment. The errors inflow stress caused by thermal effect were corrected. The effect of Zener-Hollomnparameter was analysed on the hot deformation microstructure, the peak stressequation of IN690alloy was established.(3) The microstructure evolution model was established through the high speedhot compression experiments results of IN690, such as critical strain (stress) modeland stable model and the volume of dynamic recrystallization model,and so on.(4) According to microstructure evolution model, a subroutine had beencompiled used Fortran language, which can predict the microstructure evolution ofIN690alloy. Hot extrusion process of superalloy IN690had been simulated byMSC.Superform finite element software with multi-field coupling method. Theoptimized process parameters were obtained.(5) High speed hot extrusion experiments had been finished, and the tubes withbetter microstructure and mechanical properties. The effect of deformation parameter to coincidence site lattice grain boundary volume and texture of extrusion tube hadbeen analyzed by Electron Backscattered Diffraction(EBSD).