Welded high-temperature power plant components can experience a greater risk of failure by creep during service, when compared to similar as-wrought components. The heat-affected zone (HAZ) of alloy steels is usually the region of a weldment exhibiting poor mechanical properties. The arc welding of an ASTM A470, Class 8-rotor steel in this study identified the intercritical heat affected zone (ICHAZ) as the weakest region in terms of creep rupture life. The type of welding procedure significantly affects this region, but most important are the welding parameters utilized. Because of the microstructural heterogeneity of the HAZ and sensitivity of these microstructures to changes when exposed to elevated temperatures, their performance at later times is difficult to predict. Extrapolation techniques are limited in value for predicting service lives of homogeneous materials, because these do not incorporate the microstructure changes of the materials during high temperature operation. They are even less useful for predicting the operating lives of weldments. This paper considers the creep performance and structure stability of the ICHAZ of 12 percent Cr and vanadium modified weldments produced on a retired CrMoV rotor steel. [S0094-4289(00)00303-0]
Issue Section:
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