A review of thermal, microstructural and constitutive modelling of 9Cr steel for power plant applications: Towards a through-process model for structural integrity of welded connections

Life prediction for 9Cr steel welded components is an important issue facing power plant as it moves from steady-state, base-load operation to transient, flexible operation. Welding and heat-treatment of 9Cr components alters the steel microstructure to produce a heat-affected zone, which is susceptible to early failure under creep and high-temperature cyclic conditions. Optimal welding and heat treatment processes cannot feasibly be identified experimentally but finite element simulation is a practical solution to this problem. A review of modelling methodologies for welding, heat treatment and in-service operation in thermal power plant for 9Cr steel is presented here. The authors consider that macro-scale, physically-based models are the most promising models currently available since they account for changes in material microstructure while still being practical for simulations involving component-sized FE geometries.