Creep crack growth properties of type 308 austenitic stainless steel weld metals

Using Type 308 austenitic stainless steel weld metal made by the SMAW and FCAW processes, creep tests and creep crack growth tests were carried out at a temperature of 650 degrees C. Creep crack growth rate tests were conducted using CT-type specimens and the data derived were arranged according to parameter C*. With regard to the flux cored are weld metal, Bi2O3 (melting point 820 degrees C) was intentionally added to the flux for easy slag peeling and enhanced welding operability. The bismuth segregated (segregation depth approximately 15 Angstrom) at the grain boundaries and, due to the presence of this bismuth, fracturing occurred intergranularly, with marked reduction in creep ductility. Further, the creep crack growth rate of the flux cored are weld metal, which contained large amounts of bismuth, was exceedingly rapid compared with that of SMA and FCA weld metal not containing bismuth. Bismuth that has segregated at the grain boundaries is extremely harmful with respect to creep ductility and creep crack growth properties.