MICROSTRUCTURE AND PERFORMANCE OF 1.25CR0.5MO STEEL WELDMENTS

The complex thermal cycles associated with fabrication of weldments in 1.25Cr0.5Mo steel have been documented. For the weaved welding allowed by the specified procedure, base material locations adjacent to the weld profile have been subjected to up to seven excursions above 800 degrees C during fabrication. The multiplicity of these thermal cycles resulted in a large degree of refinement within the weld metal and heat-affected zone. Creep testing has shown that the weldments produced are highly susceptible to type IV cracking, with damage in the form of cavities and microcracks developing below the specimen surface. This observation, combined with the fact that physical evidence of distress occurs relatively late in life, indicates that traditional methods of structural integrity assessment may be inadequate.