Effect of Pre-straining on the Tensile and Stress-Rupture Properties of a Novel Ni-Co Based Superalloy

For Ni-Co-based superalloys, the higher level of Co content, the lower the stacking fault energy, which promotes the formation of deformation twins and affects the mechanical properties of the materials. Mechanical tests of a novel Ni-Co-based superalloy at temperatures between 25 and 760 ℃ revealed that its strength maintained a sufficiently high level when the testing temperature was up to 650 ℃, above which the tensile strength decreased with test temperature, and there was a sharp drop at 760 ℃. Pre-strain tests at room temperature indicated that the density of dislocation and stacking faults increased with strains and they became obstacles for dislocation motion at elevated temperatures, resulting in an increase in yield strength. In addition, the grain boundary of the pre-strained specimens has a higher dislocation density than the grain interior, and dislocation recovery occurred during the stress-rupture process, resulting in a lower stress-rupture life than the sample without a pre-strain.