Cyclic creep acceleration and retardation in Cr-Mo-V rotor steel at ambient and elevated temperature respectively

The cyclic creep properties of Cr‐Mo‐V rotor steel have been explored at room temperature and elevated temperature by multiple‐step tests with increasing maximum stress (R= 0), and with subsequent tests in partial unloading (0 ≤R < 1). Cyclic creep acceleration is observed at room temperature and cyclic creep retardation at elevated temperature. This behavior is explained in terms of cyclic softening at low temperature and by creep‐dominated deformation at high temperature with a ferritic material considered especially prone to retardation because of the high diffusivity of b.c.c. material. Other interesting effects, such as strain burst phenomena and the observation of anomalously high values of the ratio of diametral strain to axial strain, are also reported.