Oxidation Behaviour of IN-738 LC Superalloys in the Presence of Ionic Salts at 1173 K

Abstract

Oxidation of the alloy having nominal composition Ni-16Cr-8.5Co(wt.%) was studied in the presence of KCl and K2CO3 at 1173 K in air. Chemical composition of oxide scales and scale morphologies were determined by means of X-ray diffraction analysis and scanning electron microscopic studies. The oxide scales of KCl- and K2CO3- coated alloys showed complex microstructures and compositions. This behaviour was ascribed to the release of volatile metallic chlorides, evolution of CO/CO2 gas as well as formation of fluxing products. The high temperature oxidation resistance is not only related to the nature of the passive film but is also strongly dependent on the salt environments and the structure of alloy.