Study On Hot Deformation Behavior And Hot Workability Of Incolocy 825 Nickel Base Alloy

Nickel base alloy was developed in the late 1930 s.It is a kind of alloy with high strength,oxidation resistance and corrosion resistance at high temperature based on nickel.It is the key material in ultra supercritical coal-fired power generation technology.For the high alloy,because of the poor thermoplasticity,the process of rolling after extrusion and opening or direct extrusion with soft steel(or stainless steel)cladding is adopted.The conventional production process includes "die casting + hot rolling + cold rolling forming",with low production efficiency.For nickel base alloy,due to the poor high-temperature thermoplasticity of nickel base alloy,the surface of slab is easy to crack during the continuous casting process,so it is impossible to realize the production of nickel base alloy through the process of "continuous casting + hot rolling + cold rolling forming".It can be said that the high-temperature thermoplasticity of nickel base alloy has become the key issue affecting the continuous casting process of nickel base alloy and whether the subsequent batch production can be realized.Based on this,the work of this paper focuses on the research of high-temperature thermoplasticity of nickel base alloy.By studying the high-temperature mechanical properties of Incoloy 825 nickel base alloy under different solid-state ratios,the constitutive equation of Incoloy 825 nickel base alloy is derived,and the temperature range of high-temperature thermal brittleness is determined,which provides experimental and theoretical reference for the development of continuous casting process of nickel base alloy.Therefore,the main work of this paper is as follows:(1)The microstructure evolution of Incoloy 825 nickel base alloy during hot compression was studied by using different parameters of deformation temperature and strain rate on Gleeble-3800.The true stress-strain curves at different deformation temperature and strain rate are obtained,and the metallographic microstructure at different parameters is obtained.The rules of recrystallization and precipitation were analyzed to understand the microstructure and mechanical properties of Incoloy 825 nickel base alloy.(2)Under the conditions of 850 ～ 1150 ℃,strain rate of 0.14s-1,0.37s-1,1s-1,2.27s-1,respectively,and deformation degree of 60%,the high temperature flow stress change of Incoloy 825 nickel base alloy with Gleeble-3800 thermal simulator was studied.The experimental data were analyzed and processed by Origin software,and the constitutive equation of inconloy 825 nickel base alloy was deduced by using Arrhenius hyperbolic sine function to calculate α,N,Q,a.the hot working diagram of inconloy825 nickel base alloy at true strain 0.1 ～ 0.8 was established based on the thermal simulation compression experiment.(3)In the temperature range of 1320 ℃ ～ 1400 ℃,the high temperature tensile test of Incoloy 825 nickel base alloy was carried out by solidification method.The inconloy 825 nickel base alloy was heated at a certain rate to a certain temperature with low solid rate for a sufficient time by Gleeble-3800 thermal simulation test machine,and then cooled to a certain temperature with a certain cooling rate for high temperature tensile deformation,with a strain rate of 3s-1.Through the analysis of experimental data and tensile fracture morphology,the zero strength temperature and zero plasticity temperature of Incoloy 825 nickel base alloy are determined,and the brittle temperature range of Incoloy 825 nickel base alloy is obtained.