Investigation on a creep-tested CB2 steel cross-weld sample welded with a matching flux-cored wire

Heavy cast components like steam turbine or valve casings made of GX13CrMoCoVNbNB9-2-1 (CB2 steel) are used in modern fossil-fired power plants for service temperatures up to 620 °C. For production welding of these huge components, high productivity and good out-of-position weldability are needed. To combine these requirements, flux-cored arc welding is a preferred welding process. A matching flux-cored wire consumable has been developed, which offers sufficient short-term mechanical properties at ambient temperature. To prove weld metal long-term properties at service temperature, uniaxial creep rupture tests at 625 °C have been started several years ago. The microstructure of a cross-weld sample, ruptured in the heat-affected zone, was investigated by light optical microscopy and scanning electron microscopy with energy dispersive X-ray analyses. Area fraction and mean radius of precipitated Laves phase and M23C6 carbides were compared to the results of MatCalc™ simulations.