INITIATION OF PWSCC OF WELD ALLOY 182

摘要

Even if Alloy 182 is usually exhibiting a high susceptibility to cracking in the laboratory, the field experience did not reveal to date a significant susceptibility to PWSCC in PWRs, when the welds have been perfectly stress relieved. However, recently, an increasing number of cracks was reported in USA, Sweden and Japan on Alloy 182 and a few cases on Alloy 82. This paper addresses the work on initiation of PWSCC engaged at EDF R&D (MAI). The main objective is to calibrate an engineering model to predict the time to initiate IGSCC vs. temperature and loading for a weld 182 having a high susceptibility to SCC crack growth. The effect of cyclic loading, strain path and dendrite orientation on initiation was also partly evaluated. Under static loading, initiation was observed down to 350 MPa at 360°C. A limited effect of cyclic loading (R = 0.9, f = 2.8 10~(-4) Hz) was observed at 360°C for a maximal stress of 350 MPa. The effect of partial periodic loading increased when the temperature decreased and when the stress increased. An empirical model predicting the time to SCC initiation was calibrated.