Carbon addition and temperature dependent tensile deformation resistance and capacity of a low-cost 3rd-generation Ni-based single crystal superalloy

A balance between the mechanical performance and castability of Ni-based single crystal superalloys is expected to be achieved by doping with appropriate carbon content. In this study, the influences of carbon content on the tensile properties of a novel low-cost 3rd-generation Ni-based single crystal superalloy at 760 °C and 1120 °C were investigated. Results showed that minor carbon addition could slightly increase the strength and plasticity of the experimental alloy at 760 °C, whereas it led to the decrease of strength and plasticity at an elevated temperature of 1120 °C. This variability was discussed in terms of the microscopic resistance for dislocation movement and the macroscopic deformation capacity associated with damage accumulation. It was found that the solid solution strength and interface strength were enhanced with increasing carbon content, however, the strength at high temperature was compromised by the enormous consumption of refractory elements, even though the precipitation of blocky M6C carbides provided additional hindrance. As for the macroscopic deformation capacity, interdendritic carbides could hinder the extension and/or trigger the activation of slip bands at 760 °C. Nonetheless, the initiation tendency and propagation behavior of microcracks at 1120 °C were facilitated due to the strong stress concentration and severe deformation incompatibility of interdendritic carbides. Overall, future compositional optimization should focus on reducing the formation of Ta-enriched MC carbides to minimize the loss of refractory element reinforcement and the reduction of deformability at high temperatures.