THE USE OF COATINGS FOR HOT CORROSION AND EROSION PROTECTION IN TURBINE HOT SECTION COMPONENTS

Abstract

High pressure turbine components are subjected to a wide variety of thermal and mechanical loading during service. In addition, the components are exposed to a highly oxidizing atmosphere which may contain contaminants such as sulphates, chlorides and sulphuorous gases along with erosive media. So the variety of surface coatings and deposition processes available for the protection of blade and vane components in gas turbines are summarised in this study. Coating types range from simple diffusion aluminides to modified aluminides and a CoCrAlY overlayer. The recommendations for corrosion-resistant coatings (for low temperature and high temperature hot corrosion environments) are as follows: silicon aluminide and platinumchromium aluminide for different gas turbine section superalloys substrates. Platinum metal additions are used to improve the properties of coatings on turbine components. Inorganic coatings based on ceramic films which contain aluminium or aluminium and silicon are very effective in engines and gas turbines. Diffusion, overlayer and thermal barrier coatings which are deposited on superalloys gas turbine components by pack cementation, plasma spraying processes and a number of chemical vapour deposition, physical vapour deposition processes (such as electron beam, sputtering, ion plating) are described. The principles underlying the development of protective coatings serve as a useful guide in the choice of coatings for other high temperature applications.

Keywords

• Turbine gas section, Hot corrosion, Protective coatings, Thermal coating

SICAK TÜRBİN PARÇALARINDA SICAK KOROZYONDAN VE EROZYONDAN KORUNMA İÇİN KAPLAMALARIN KULLANIMI

Öz

Yüksek sıcaklık türbin malzemeleri sülfat ve klorürle birlikte aşındırıcı partiküllerin bulunduğu ortamda termal ve mekaniksel yüklenmeyle karşı karşıyadırlar. Bu incelemede gaz türbinlerinde kullanılan parçaların korunması için mevcut olan çeşitli kaplama ve biriktirme prosesleri özetlenmiştir. Basit diffüzyon kaplamadan modifiye alüminyum kaplamaya ve CoCrAlY tabakalı kaplamaya kadar birçok kaplama türü vardır. Koruyucu kaplamaların geliştirilmesinin altında yatan prensipler, diğer yüksek sıcaklık uygulamaları için kaplamaların geliştirilmesi ve seçiminde kullanışlı rehber olarak hizmet verir.

Anahtar Kelimeler

• Gaz türbin ünitesi, Sıcak korozyon, Koruyucu kaplama, Termal kaplama