A numerical study on the influence of grain boundary oxides on dwell fatigue crack growth of a nickel-based superalloy  

作　　者：C.Z.Fang H.C.Basoalto M.J.Anderson H.Y.Li S.J.Williams P.Bowen 

机构地区：[1]Department of Materials Science and Engineering,University of Sheffield,Mappin St,Sheffield S13JD,UK [2]School of Metallurgy and Materials,University of Birmingham,Edgbaston,Birmingham B152TT,UK [3]Institute of Structural Materials,Swansea University,Swansea SA18EN,UK

出　　处：《Journal of Materials Science & Technology》2022年第9期224-235,共12页材料科学技术（英文版）

摘　　要：A theoretical treatment on the oxide-controlled dwell fatigue crack growth of aγ'strengthened nickelbased superalloys is presented.In particular,this study investigates the influence of an externally applied load and variations in theγ'dispersion on the grain boundary oxide growth kinetics.A dislocation-based viscoplastic constitutive description for high temperature deformation is used to simulate the stress state evolution in the vicinity of a crack at elevated temperature.The viscoplastic model explicitly accounts for multimodalγ'particle size distributions.A multicomponent mass transport formulation is used to simulate the formation/evolution of an oxide wedge ahead of the crack tip,where stress-assisted vacancy diffusion is assumed to operate.The resulting set of constitutive and mass transport equations have been implemented within a finite element scheme.Comparison of predicted compositional fields across the matrix/oxide interface are compared with experiments and shown to be in good agreement.Simulations indicate that the presence of a fineγ'size distribution has a strong influence on the predicted ow stress of the material and consequently on the relaxation in the vicinity of the crack-tip/oxide wedge.It is shown that a unimodal dispersion leads to reduced oxide growth rates(parabolic behavior)when compared to a bimodal one.Stability conditions for oxide formation are investigated and is associated with the prediction of compressive stresses within the oxide layer just ahead of the crack tip,which become progressively negative as the oxide wedge develops.However,mechanical equilibrium requirements induce tensile stresses at the tip of the oxide wedge,where failure of the oxide is predicted.The time taken to reach this critical stress for oxide failure has been calculated,from which dwell crack growth rates are computationally derived.The predicted rates are shown to be in good agreement with available experimental data.

关 键 词：Nickel based superalloy Dwell crack growth Gamma prime Creep Oxidation Dislocation-based modeling Multicomponent diffusion Finite element method 

分 类 号：TG132.3[一般工业技术—材料科学与工程]