Strain Relaxation and Recovery Test (SRRT) on Waspaloy for Measuring Irreversible Strain Rate Equivalent to Minimum Creep Rate

It is shown that the stress dependence of the irreversible, average viscous strain rate during decelerating (primary) creep measured by the Strain Relaxation and Recovery Test (SRRT), from 725 to 315 MPa, corresponds well with that of the minimum creep rate in the stress range 650-450 MPa for forged nickel-based Waspaloy at 732 °C (0.62Tm). Both the viscous strain rate and the minimum creep rate obey a power-law dependence on stress with a stress exponent of 11. Since creep tests are time consuming and require many samples, usually only a limited number of data are generated. However, it is shown that the SRRT can generate a large data base over a wide stress range in a short time, using only one specimen, and, therefore, providing a cost-effective way to evaluate material performance at high temperatures. A method is also described for establishing design curves using SRRT data.