Creep rupture properties of welded joints of heat resistant steels

In this study, mechanical and creep rupture properties on similar welded joints of Grade 91 steel (Mod.9Cr-1Mo) and dissimilar welded joints of Grade 91 / Incone182 / SUS304 were examined at elevated temperatures. The effects of temperature and stress on the failure location of welded joints were also investigated. Creep rupture tests were conducted at three temperature levels: 823, 873, and 923 K, the stress ranged from 160 to 240 MPa, 80 to 160 MPa, and 40 to 80 MPa respectively. The creep-rupture strength of the specimen with welded joints was lower than that of the test specimen of base metal at all temperature levels. In addition, the differences in creep strength between the welded joint specimen and the base metal specimen to be greater at higher temperature levels. The fracture Type, observed after long-term creep rupture tests on dissimilar welded joints was transformed from a Type V fracture and a Type VII fracture to a Type IV fracture. It was determined that the fracture type of the 100,000 hours ruptures strength at 823K and 873K for dissimilar welded joint were Type IV fracture.