High-Temperature Oxidation Properties of MCrAlY Coatings Formed by Atmospheric Plasma Spraying

Abstract

MCrAlY alloy thermal spray coatings are applied to protect the substrate from oxidation and corrosion under high temperature environment. Various MCrAlY alloys can be coated by different thermal spray processes; LPS, HVOF, and APS. MCrAlY coating by APS is said to be inferior in oxidation resistance, however few studies have been conducted on oxidation property of APS MCrAlY alloy coatings. In this study, CoNiCrAlY, NiCoCrAlY, and NiCrAlY alloys of two different particle sizes were prepared and their coatings were formed by APS process. These MCrAlY alloy powders and coatings were exposed to high temperature and their surface oxide formations were analyzed to determine the growth rate and the activation energy from the growth of the oxide layer thickness. Furthermore, microstructure observations and chemical composition analysis of coatings were conducted. From these results, influence of MCrAlY powder size difference and oxides contained in the coating on high temperature oxidation property of APS MCrAlY coatings was revealed.