Hot corrosion behavior of nickel-base cast superalloys was studied for 10 alloys at 900°C for 7 h in the combustion gas flowing at Mach 0.5 prepared from 5 ppm NaCl-containing air and 0.5% sulfur-Containing fuel. It was classified into two discrete types. The first was characterized by a heavy uniform attack forming thin Cr-, Al-and Ti-depleted zone. Extent of the attack was independent of Cr content. The second was characterized by moderate localized attack forming thick Cr-, Al-and Ti-depleted zone and extent of the attack decreased with increasing Cr content. The first was observed for lower Cr alloys and the second for higher Cr alloys. However, the corrosion for alloys with intermediate Cr content was influenced also by other alloying elements. The type of the corrosion expected for an alloy depends on whether it forms a protective layer of chromium rich oxide or not.
