Creep Strength of Chromium-Containing Conventional and ODS Steels in Oxygen-Controlled Pb at 650°C

Two martensitic conventional steels, T91 (modified 9Cr1Mo) and P92 (NF616), and two ODS steels with 12 and 14 mass.% chromium content were subjected to creep-rupture tests in stagnant oxygen-controlled Pb with c_o = 10⁻⁶ mass.% at 650°C. The 9Cr conventional steels were tested in liquid metal at 75–200 MPa, while the stress for the tests of ODS steels were chosen in the range of 190–400 MPa. Reference tests were carried out in stagnant air under similar loading. Both ODS steels show obvious change in secondary creep rate and failure appearance at 330–350 MPa, while the martensitic steel P92 tested in Pb at 75 MPa (t_R = 13,090h) shows a significant drop in creep strength accompanying with a change from ductile to brittle fracture and a considerably reduced necking. Effects of microstructure evolution during the exposure at the elevated temperature and risk of LME due to a direct contact to liquid metal are discussed.