Isothermal Oxidation of Simple and Pt-Modified Diffusion Coating on Inconel Alloy 600 In Water Vapor

Abstract

In this work the oxidation behavior of both inconel alloy 600 and coated system(Pt-modified aluminide coating) was investigated in pure water vapor H2O in thetemperature range 700 - 900 ºC. The platinum was deposited by electrochemicalmethod. Pt-modified aluminide coating was applied to inconel alloy 600 by using singlestephigh activity pack cementation method. The weight gain measurements indicatethat the oxidation kinetic is parabolic for uncoated and coated alloy. At temperaturesbelow 900 ºC the inconel alloy 600 is less aggravated in water vapor environmentsbecause it is a chromia former alloy. At 700 ºC, water vapor does not have a significanteffect on the spalling of oxide scales. At 900 ºC, water vapor causes spalling of theoxide scales during isothermal oxidation of inconel alloy 600. Therefore, it is concludedthat this alloy should not be used above 900 ºC in water vapor environments. Largevoids were found at the oxide scales-substrate interface and at grains or at grainboundaries due to the chromium outward diffusion toward the oxide scales.At 900 ºC, the parabolic rate constant (kp) of the coated system was one order ofmagnitude lower than that for the uncoated alloy. It was concluded that, water vaporexhibit little effect on the Pt-modified aluminide coating. Oxide phases that formed oncoated system are: Al2O3, NiAl2O4, Cr2O3, and NiFe2O4.