Abstract
Macroscopic study, magnetic susceptibility measurement, bulk carbon analysis of different regions of the weld, hardness measurement, chemical composition, and Energy Dispersive X-Ray Analysis (EDAX) were carried out. Localized carburization in the weld regions, formation of grain boundary carbides and grey phase, hardness at carburized locations, and creep cavities/cracks were observed. EDAX revealed brittle grey phase formed at grain boundaries rich in Mn and Cr.
Initiation of weld cracking was from its root. This was caused by carburization of the root of the weld and the formation of brittle grey phase at grain boundaries through their embrittling effects. Propagation of cracks was assisted by enhanced creep due to stress concentration at crack tips and higher stresses caused by decreasing load bearing area of the weld with the progress of the fracture and formation of brittle grey phase at grain boundaries.