Tensile creep behavior and strain-rate sensitivity of superalloy GH4049 at elevated temperatures

According to the working temperature and load of superalloy GH4049 in an aero-engine, we systematically study its high temperature mechanical behaviors that have crucial effects on component life. Creep tests are performed in the stress range of 137-600 MPa and the temperature range of 700-900 degrees C. The strain-rate sensitivities (SRSs) under simple tension, fatigue and creep conditions are also analyzed in detail at 600 degrees C, 768 degrees C and 832 degrees C, the working temperatures at typical positions on the turbine blade. Through creep experiments of GH4049 under single- and multistage loading conditions, we obtain the relationship between the minimum creep rate and the rupture time, the effect of high temperature strain recovery after creep and the effect of warm-working at high temperatures on the subsequent room-temperature strength. In the SRS analysis, we achieve the SRS indexes under different experimental conditions Meanwhile, we generalize the SRS definition from simple tension to low-cycle fatigue (LCF) and multistage creep conditions, and verify the validity of these generalizations. The verifications illustrate that the SRS definitions in this paper can quantitatively describe the strain-rate dependence behaviors under LCF and multistage creep. All these fundamental works establish the basis of complex mechanical behavior simulations for GH4049 and the basis of the analysis of structural integrity and reliability. (C) 2009 Elsevier B.V. All rights reserved.