Effect of carbon content on microstructure and tensile properties of Ni-based GH3230 superalloy

This present work investigates the dependence of carbon (C) content variation (0.074 wt%, 0.1 wt%, 0.15 wt%) on the microstructure and tensile properties of GH3230 superalloy at 23 degrees C and 950 degrees C. The results show that the variation in C content did not change the type of precipitated particles, and all the variants included M6C and M23C6. Moreover, the increase in C content preferred to increase the volume fraction of M23C6 and promoted the formation of clusters within the grains as well as the formation of lamellae or films at grain boundaries. The tensile properties at 23 degrees C indicated that the increase in C content significantly improved the yield strength (YS), and the evaluation of the strengthening mechanism revealed that the contribution of carbide particle strengthening was the main reason for the strength enhancement. Meanwhile, due to the dual effects of uniform carbide distribution and grain refinement, the plasticity peaked at the C content of 0.1 wt%. At 950 degrees C, the strengths of the three C content variants remained at similar levels, and the plasticity declined severely with the increase in C content. Fracture characterization revealed that the increase in C content accelerates the dynamic recovery and dynamic recrystallization (DRX) process. The grain boundary weakening effect of fine DRX grains and the increase of the phase interface between DRX grains and high-volume fraction carbides accelerate the stress concentration and crack development, which leads to the severe reduction of plasticity.