Abradable Plasma Coatings from Mechanochemically Alloyed Aluminum Powder for Gas Turbine Engines

Abradable coatings are used in modern gas turbine engines to minimise clearances and reduce gas leakage through the blade tips. The development of wear-resistant coatings for turbine casings is challenging due to the high-temperature operating conditions and aggressive fuel combustion products. The balance between erosion and abrasion resistance of coatings necessitates the search for new optimal solutions. This article discusses the properties of two new abradable coatings based on composite powders. The composite powders were synthesised by mechanochemical alloying of aluminium, silicon (8%) and boron nitride (20%). The main component were industrial aluminium powders of two types, obtained by spraying primary aluminium melt, with a rounded and elongated shape, which affected the porosity of the sprayed coatings, which was 2.8% and 9.5%, respectively. The prepared powder was coated by Atmospheric Plasma Spraying (APS) with generating a laminar plasma jet. As a result, abradable coatings with the required set of performance properties were obtained. Emphasis is placed to the structure, chemical composition, and microhardness of coatings made of round and elongated powders. The resulting coatings can be recommended for use as abradable coatings. Among the considered coatings, elongated powder coatings have higher hardness and potentially higher abrasive and erosion resistance for high-temperature turbines.