Study On Creep Properties Of GH3128 Superalloy Cooling Tube In Intermediate Heat Exchanger

Nickel-base superalloys are the key hot-end components of modern aero-engines,spacecraft and rocket transmitters,as well as naval vessels and industrial gas turbines(such as turbine blades,guide blades,combustion chambers,etc.).They are also important high-temperature structural material for nuclear reactors,chemical equipment,coal conversion technology and other working conditions under very harsh conditions.In this paper,GH3128 high-temperature nickel-base alloy is taken as the research object to study its creep behavior at high temperature.The main research contents are as follows:The Gleeble3800 thermal simulation test machine was used to conduct the high-temperature creep tensile test,and the creep behavior of GH3128 nickel-base superalloy was analyzed under the condition of high temperature.The reasonable high-temperature creep theory was selected,and the collected data was fitted by Origin9.0software to draw the strain-time curve.The creep model was determined,the parameters of the equation were established by linear fitting of the test data,and the creep constitutive equation of GH3128 at high temperature was obtained.The experimental data under different temperatures and different stresses were compared with those calculated by constitutive equation.The result showed that the experimental data were in good agreement with the calculated values.Norton creep damage theory based on ? extrapolation method and Kachanov-Rohatnov creep damage theory were used to analyzed creep damage of GH3128 high temperature nickel-base alloy at 950?,and the damage factors calculated by the two methods were compared.The Norton creep model in the finite element software was used to simulate the test process,and it was found that the creep model in the finite element software could not reflect the whole creep process well.A damage-hardening creep model was established for high temperature nickel-base alloy GH3128,and the program containing damage-hardening creep model was written to ANSYS,by UPFs.The experimental results simulated by this model were compared with the experimental data.Taking the cooling pipe of HTR-10 intermediate heat exchanger as example,when the material of cooling pipe was GH3128 high temperature nickel-base alloy,the three-dimensional stress in the cooling pipe was analyzed,and the three-dimensional stress and elastic stress after considering creep effect were calculated and compared.After considering the creep effect,the wall thickness and the mean radius were changed,and the stress changing in the cooling pipe were compared and analyzed.The creep buckling analysis of cooling pipe was carried out.The creep equation was used to simulate the model by finite element method.The curve of the wall strain changing with time was selected and the critical time of creep buckling was solved by ‘maximum point of curvature' method.The critical time of creep buckling was analyzed by changing the thickness and the mean radius of pipe wall.