Microstructural evolution and tensile property of 1Cr15Ni36W3Ti superalloy during thermal exposure

1Cr15Ni36W3Ti was thermally exposed at 580 degrees C and 680 degrees C, respectively, up to 3000 h. The gamma' phase and intergranular TiC carbides continuously coarsened during exposure. None of eta, laves or sigma phase was discovered in the exposed samples, indicating good microstructure stability under the present exposure conditions. The ripening process of the gamma' phase could be well modelled utilizing the LSW theory. The evolutions of the yield and tensile strengths were monotonous during exposure at 580 degrees C. However, a transition point in strengths was detected in the tensile samples exposed at 680 degrees C for 300 h. Accordingly, the critical gamma' diameter was measured to be 13-14 nm. The gamma'/dislocations interaction mechanism transformed from shearing to looping with the gamma' diameter exceeding the critical point. The combination of the weakly coupled dislocations model and the Orowan looping model yielded a critical diameter of 13.1 nm which coincided well with the measured one, indicating the applicability of these two strengthening models for 1Cr15Ni36W3Ti. The present exposure conditions did not exert a profound effect on the fracture mode. All the tensile samples underwent a typically ductile fracture with a dimple pattern dominating the fracture surface. The dispersed deformation induced by the prevalence of dislocation looping in the over-aged tensile samples retarded the propagation of intergranular cracks. The declined precipitation hardening increment and the enhanced deformation homogeneity partially recovered the tensile ductility in the over-aged samples exposed at 680 degrees C. (C) 2021 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

1Cr15Ni36W3Ti was thermally exposed at 580°C and 680°C for up to 3000 hours. The gamma' phase and intergranular TiC carbides coarsened continuously, while no eta, laves, or sigma phases were found, indicating good microstructure stability. The evolution of strength was monotonic at 580°C, but a transition point was detected at 680°C after 300 hours of exposure. The interaction mechanism between gamma' and dislocations shifted from shearing to looping after reaching a critical diameter of 13-14 nm.