MICROSTRUCTURAL EVOLUTION IN THE HEAT-AFFECTED ZONE Cr-Mo STEELS ON WELDING AND UPON SUBSEQUENT THERMAL EXPOSURE.

This microstructural work was aimed at correlating the properties with carbon content and thermal exposure. SEM examination revealed the dependence of microconstituent morphology on prior material history. To obtain information on the type, size, morphology, distribution, and composition of the alloy carbides present, STEM examination of carbide extraction replicas taken from specimens was also conducted. An insight into stress-rupture strength and ductility will be gained from the proposed mechanisms for the effects of carbides and microstructure on behavior. The work is based on a large body of stress-rupture data obtained for annealed, normalized and quenched and tempered specimens, with and without service exposure.