The effect of the lower stress level on the cyclic creep behavior of an ods superalloy

Cyclic creep and stress rupture results are reported and discussed as a function of the lower applied load for INCONEL MA6000, which is a mechanically alloyed oxide dispersion strengthened (ODS) and γ’ precipitation strengthened nickel-base superalloy. In prior work, very large decreases in the effective minimum cyclic creep rate, based on time at maximum load, were found to occur for cyclic creep testing using a lower load near zero. The present results show that this decrease in creep rate depends on the value of the lower load. As the lower load increases, the cyclic creep rate increases proportionally, but remains less than the corresponding static creep rate. The values of the cyclic creep rates are shown to be related to the magnitude of the anelastic strain recovery occurring during the lower load portion of the cyclic creep test. The results are also used to improve on the anelastic relaxation model for cyclic creep of materials with strong pinning points. INCONEL is a trademark of the INCO family of companies formerly Associate Research Scientist with Columbia University