Transformation and tempering behavior of 12Cr-1Mo-0.3V martensitic stainless steel weldments

Abstract Autogenous, bead-on-plate gas tungsten-arc (GTA) and laser welds in a 12Cr-1Mo-0.3V (HT9) martensitic stainless steel were evaluated using both optical metallography and microhardness techniques. The as-welded fusion zone microstructures consisted of a mixture of untempered martensite and metastable delta ferrite and exhibited a hardness in the range of R c 48–55. Four distinct microstruetural regions were identified in the heat-affected zone (HAZ) of the GTA welds and could be related to specific phase regions on the equilibrium phase diagram. The tempering behavior of the GTA and laser welds was similar. The tempering response was relatively sluggish at temperatures below 600°C (1110°F). Tempering for 1 hour at 800°C (1470°F) reduced the hardness of both the fusion zone and HAZ to the level of the quenched and tempered base metal.