A Survey of the Corrosion Behaviour of DIN 2.4663 in PNP Standard Helium at 700-900 C

Over 100 corrosion specimens taken from 13 casts of Inconel 617 have been examined after exposure in PNP standard helium at 700-900°C The results of weight change measurements, carbon pick up and micro examination are presented in this report. After initial carbon pick up good protection against carburisation occurs. However, a slow and continuing rise in the thickness of both surface scale and internal oxidation has been found Some significant variations occur between the casts in overall levels of both carburisation and oxidation. This current survey includes two casts of Inconel 617 that have been fabricated to the same dimensions as production intermediate heat exchanger tubing. The influence of surface finish has been examined and results suggest that faster internal oxidation occurs on the as-produced tubing surfaces than on a cut specimen surface. (author)