Tensile Creep Properties and Damage Mechanisms of W-4Re-0.27HfC Alloy at 1500-1700C

In this paper, the tensile creep behavior in vacuum of W-4Re-0.27HfC alloy prepared by powder metallurgy was studied, the creep temperature was 1500-1700 degrees C and the creep stress was 40-60 MPa. SEM, EBSD and TEM technologies were used to observe the microstructure, and characterize the evolution of grain size and dislocation during the creep process. The results show that the steady creep rate of W-4Re-0.27HfC alloy ranges from 1.10(-7) s(-1) to 5.10(-6) s(-1), which is 1-2 orders of magnitude lower than that of pure tungsten (W). The reason of that the creep resistance of W-4Re-0.27HfC alloy is higher than that of pure W is the dislocation pinning by HfC particles and the lattice distortion caused by Re replacing W atoms. The creep mechanisms of W-4Re-0.27HfC at 1500 degrees C are mainly atomic diffusion and grain boundary slip, accompanied by dislocation slip, dislocation climb becomes the main creep mechanism with the temperature increasing. The dislocations are blocked by the HfC particles, which leads to the debonding of the HfC/matrix interface. Moreover, the desquamation of HfC particles forms pores, which results in the great degradation in the creep properties.