Creep Deformation and Rupture Behaviour of P92 Steel at 923 K

Creep deformation and rupture behaviour of P92 steel has been examined at 923 K for stresses ranging from 75 to 150 MPa. The steel exhibited well defined primary, secondary characterized by minimum creep rate and prolonged tertiary creep stages. The stress dependence of minimum creep rate obeyed Norton's power law and exhibited distinct stress regimes characterised by separate values of stress exponents in low and high stress regimes. Similarly, the stress dependence of rupture life also obeyed power law and displayed two stress regimes with separate stress exponent values. The steel displayed decrease in creep ductility with increase in rupture life in the low stress regime and followed generalised Monkman-Grant relation interrelating minimum creep rate and rupture life. Modified Monkman-Grant relation has been found to be valid for the steel. Fractographic examination indicated dominance of transgranular fracture on the fracture surfaces of tested specimens.