High Temperature Stability of Pack Aluminide Coatings on IN738LC

Abstract

Development of gas turbine blading alloys over the past two decades has conferred greatly increased high temperature strength to these materials but generally at the expense of oxidation and corrosion resistance. To enable cheaper, less pure fuels to be burnt in high performance gas turbines it is often necessary to improve surface integrity by the use of protective coatings. This paper describes the formation of typical commercial pack aluminide coatings and examines the subsequent behaviour of two specific variants upon prolonged high temperature exposure. The degeneration of the coating layer of a simple coating is illustrated and the improvements resulting from the addition of Pt to the coating layer are demonstrated.