High nickel alloys and various analyses of Types 304L, 316 and 347 as well as European commercial steels off similar analysis were tested in high temperature (350 C - 662 F) demineralized water and steam (650 C - 1202 F) for varying periods up to five months. High-nickel austenites were found susceptible to intergranular stress corrosion cracking different from the transgranular cracking known to occur in austenitic stainless steels
Tests in 650 C steam show cracking of high nickel alloys increased with slight plastic deformation while 18-10 and 20-25 stainless were unaffected. It was found also that severe intergranular attack was observed in the high nickel alloys subjected to highly oxidizing acid media. Authors postulate that a structural element in these susceptible alloys is responsible.
Discussors suggest that lead or oxygen contamination of test water may have contributed to results reported, which are at variance with numerous test and service results of the same material in like environments. Authors contend lead could not be detected in experiments performed later to check influence of this contaminant and that oxygen content was ≤ 0.003 mg/l, equal to sensitivity of analytical method.
Authors hypothesize cracking observed is function of impurities concentrations at grain boundaries and contend satisfactory industrial experience with Inconel 600 can be attributed to low stresses in service.
