METHOD OF NONDESTRUCTIVE EXAMINATION OF CHROMIUM-CONTAINING NICKEL-BASED ALLOY FOR GRAIN BOUNDARY CORROSION AND EXAMINATION APPARATUS

摘要

Conventional methods of examining chromium-containing nickel-based alloys,such as Inconel 600 alloy, for chromium-deficient phases necessitate surfacecorrosion or cutting and hence are methods accompanied by destruction andcontrary to the idea of nondestructive examination. The information obtainablewith the methods has been limited to one concerning surface chromium-deficientphases. The method, which is for examining a chromium-containing nickel-basedalloy for grain boundary corrosion based on thermal sensitization, comprises:measuring the saturation magnetization Ms(Ti) of a test piece at each oftemperatures distributed at the same interval throughout the range of from theminimum to the maximum Curie temperatures corresponding to the chromiumconcentrations in the chromium-deficient phase of the alloy; andquantitatively determining the average spatial distribution of the chromium-deficient phase of the test piece, i.e., the volumes for respective chromiumconcentrations of the chromium-deficient phase at around grain boundaries,using a given arithmetic expression.