EFFECT OF THERMAL SHOCK ON DISSIMILAR WELD

Abstract

For a long time now, dissimilar welds have been a necessity within the pressurized water reactors and boiling water reactor designs, where the heavy section low alloy steel components are usually connected to stainless steel primary piping systems. For pressurized water reactors, the dissimilar welds, which are of particular interest, are those attaching the systems to the various nozzles of the reactor pressure vessel, steam generators and pressuriser. Welding is done between SA 516 ferritic steel and 304L stainless steel using 309L stainless steel as buttering layer material and 308L stainless steel as filler material. Thermal shock is given for 200 cycles between the temperature ranges of 25- 600 ° C. Tensile test is carried out which shows the decrease in yield strength and ultimate tensile strength after thermal shock. Impact strength also decreases after thermal shock. While hardness of SA 516 and S.S 304L increases, weld zone doesn't have much effect of thermal shock on hardness. While hardness of buttering layer significantly decreases. Optical microscopy, SEM fractography and FESEM analysis are carried out. In which we found crack generation at the SS 304L- weld interface and buttering layer- weld interface.