Abstract
The high temperature performance of dissimilar metal welds betweenferritic and austenitic materials is directly influenced by a number of material and operational factors. The welds are heterogeneous and metallurgically complex, and their performance is not well understood. The present work specifically examines the effect of slow thermal cycles on the high temperature creep behaviour of two 2·25Cr–1Mo/type 316 alloy welds: one using a type 316 filler and one using a high nickel filler metal. A third, all stainless steel weldment was also tested for comparison purposes. A vessel containing the three test welds was manufactured and strain gauges were positioned axially across the interface of each weld. This vessel was then pressurised and subjected to three different types of test cycle, each including a holding period. Twenty three separate cycles were used and the vessel was destructively examined after completion of the test period. Results indicate that the similar metal weldment exhibited behaviour typical of that expectedfor creep of a plain cylinder loaded by internal pressure. Datafrom the dissimilar weldments were different, with the creep performance affected by the mismatching properties. The observed behaviour is rationalised, with the aid of available stress analysis, based on differences in both physical and creep properties of the constituent materials.
MST/1946
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