In situ proton irradiation creep of ferritic–martensitic steel T91

An irradiation creep apparatus was developed for in situ straining of T91 strip samples while exposed to 2–3 MeV proton irradiation at 300–600 °C. Thermal creep experiments were conducted at 600 °C, 47 MPa, and 500 °C, 160 MPa. The thermal creep strains were in reasonable agreement with literature data on bulk samples of T91. An irradiation creep experiment was conducted at 500 °C and 160 MPa with a damage rate range from 3.1 × 10−6 dpa/s to 4.9 × 10−6 dpa/s. The creep rate of T91 was found to increase linearly with dose rate. A TEM investigation of the irradiated microstructure showed signs of dislocation pileup, subgrain formation, and small dislocation loops. The results illustrate the utility of accelerator-creep experiments to obtain creep rates at low dose and the capability to observe transient changes in real time, thus providing the tools for isolating the effects of individual variables on creep rate of T91.