STUDY ON GROWTH DIRECTION AND CHARACTERISTICS OF SCC IN NICKEL BASE WELD METAL IN HIGH TEMPERATURE OXYGENATED WATER

摘要

SCC growth direction and SCC characteristics in Ni base weld metal (DNiCrFe-1J) in high temperature oxygenated water have been studied. The following results were obtained. (1) Strong direction dependence was observed in which SCC propagated preferentially along the growth direction of columnar crystals, (2) Conventional average SCC length which can be calculated from the equation in which SCC area is divided by the entire CT specimen thickness was about 1/2-3/4 times the average individual SCC length on individual columnar crystals. This was because SCC does not go through the entire thickness of the CT specimen. On the other hand, maximum SCC length was almost equal to the average individual SCC length produced on individual columnar crystals. Thus, the average individual SCC length and/or maximum SCC length were judged to be appropriate lengths for obtaining the SCC growth rate of Ni base weld metal (DNiCrFe-1J).