Fracture Toughness Characterization of Mod.9Cr-1Mo Welds

The fracture toughness of the weld metal is crucial for the integrity of components as it is often been identified as the region prone to easy crack initiation and growth. To this end, fracture toughness characterization of Mod.9Cr-1Mo welds have been carried out, where the TIG and A-TIG processes were adopted as the welding procedures. The J–R curves at room temperature were determined using CT specimens, fabricated from the weld pads as well as from the base material. The average J0.2 value for the base material and the TIG weld were 180 kJ/m2 and 177 kJ/m2, respectively. For A-TIG welds, a brittle fracture was observed with a negligible crack extension (less than 0.1 mm). Signatures of cleavage fracture, as observed in the SEM fractographs of the A-TIG weld, corroborates well with the above observation. In contrast, the fractographs of the TIG weld has shown dimples indicating a ductile fracture. For A-TIG welds, since valid J–R curves could not be obtained, average fracture stress was determined to be ~2 kN m−2.