Role of Mo in the nucleation of intermetallic laves phase

Abstract

The present research work investigates the effect of the re-austenitizing based post-welded tempering (PWNT) treatment on microstructure evolution and fracture characteristics of the P91 welds joint under creep exposure condition. The major problem associated with the P91 welded joint is the failure from the soft inter-critical heat affected zone (ICHAZ) during elevated creep service conditions. The failure is associated with the altering of the microstructure of the P91 steel as a result of the welding heat, which leads to the formation of ICHAZ. To investigate the creep performance of the welded joint, creep tests have been conducted at 620 °C for applied stress of 200 MPa (PWNT 1) and 150 MPa (PWNT 2). The crept specimen was carried out in detail by using the scanning electron microscope (SEM). The PWNT have observed a significant effect on fracture characteristic, and it shifted from the soft ICHAZ to over-tempered base zone. The inter-metallic Laves phase was observed in each region of the weldments for specimen exposed at 620 °C for applied stress of 150 MPa (PWNT 2).