Oxidation and hot corrosion behavior of sputtered nanocrystalline coating of superalloy K52

Nanocrystalline coating on the cast K52 alloy was prepared by magnetron sputtering from the target of the same alloy. The comparison of oxidation in air at 800-1000 degrees C and hot corrosion under molten Na2SO4+25 wt.% K2SO4 at 850 degrees C of the cast alloy and its nano-grained counterpart was investigated by means of TGA and XRD. The result showed that the nanocrystallization of the cast alloy led to a transformation of the alloy from a chromia former to an alumina former, and consequently a greatly reduced oxidation rate. Besides, the alumina scale formed on the nanocrystalline coating was much adherent compared to the chromia scale on the cast alloy. In contrast, the increase of the hot corrosion resistance was not significant for the nanocoating with regard to the cast alloy. (C) 2007 Elsevier B.V. All rights reserved.