Study On Creep Damage Behavior Of Nickel-based Single Crystal Superalloy

Aero engine turbine blades serve in complex and harsh environments such as uneven temperature fields,stress fields and high temperature oxidation,long-term、high temperatures and stresses can lead to blade tissue degradation and mechanical properties degradation.Considering that creep damage is one of the main forms of damage to turbine blades,it is of great significance to carry out research related to the assessment of blade tissue degradation-creep residual life to ensure the safe service of aero engine blades and reduce maintenance costs.The microstructure damage characteristics of DD413 alloy under thermal-force coupling were simulated by interrupt creep experiments and quantified.The microstructure damage characteristics of DD413 alloy under the action of thermal-mechanical coupling were simulated by interrupted creep experiments and quantitatively characterized;The effects of creep damage microstructure under different pre-strains on the re-creep properties of DD413 alloy at980℃/200 MPa and 870℃/430 MPa were comparatively studied,and the relationship between the microstructure damage parameters and the re-creep properties was established.The creep interruption experiment of DD413 alloy under different thermal-force coupling effects,the γ’ strengthening phase has degenerated to varying degrees.Tissue degeneration damage in the γ’ phase mainly includes a decrease in the volume fraction of the γ’ phase,a decrease in the cubic degree of the γ’ phase and an increase in the degree of rafting of the γ’phase.Compared with the cross-sectional structure,it can be seen that compared with the heat treatment state,the degradation of the γ’ phase of the alloy is mainly manifested by the coarse connection of the γ’ phase and the dissolution of the γ’ phase.After creep deformation at 870°C,its γ’ phase corners become rounded and the volume fraction decreases slightly.As the stress increases,the phenomenon of γ’ connected becomes more and more pronounced.When the plastic response variables are the same,the tissue degradation is more serious after the high temperature creep deformation of the alloy at 980°C,and its volume fraction also shows a decreasing trend with the increase of the response variable.Comparative observation of longitudinal section tissue shows that under the action of different thermal-force coupling,the raft drainage of the alloy longitudinal section structure has undergone different degrees,which corresponds to the phenomenon of cross-sectional γ’ connection.Under the same temperature and stress conditions,as the plastic stress variable increases,the degree of raft row of alloy γ’phase gradually increases.Based on the creep degradation tissue parameter,the degree of microstructure degradation after thermal-force coupling is divided into four levels: severe degradation,secondary severe degradation,moderate degradation and mild degradation.Comparing the tissue rescrew properties of different creep damage,it is found that the degree of tissue damage of alloy 980°C creep is greater than that of 870°C,and the corresponding recreep performance after creep damage is worse.Combined with the quantitative damage characterization results of microscopic tissues,it can be seen that raft drainage is the main reason for the decrease in creep performance of alloys.Compared with raft drainage,the decrease in the volume fraction of the γ’ phase has little effect on the creep properties of the alloy.