HVOF spraying has established itself in the last decade as a very cost competitive method, increasingly replacing VPS/LPPS for the application of typical high temperature protective metallic coatings on IGT hot gas path components. In order to further improve this technology, ALSTOM recently developed a new design of a 4-injector-block for the K2-gun. This advanced design does not only significantly optimize the energy consumption and spraying time, but also enables the future application of new complex metallic coatings. A CFD simulation of the K2-gun was performed in order to identify the optimization potential. Based on the results, an improved prototype was manufactured, validated and successfully introduced into manufacturing. The aim of the study was also to investigate in detail the impact of the hardware modification on parameters such as spray spot geometry, deposition efficiency, fuel consumption and the corresponding coating quality (porosity, bonding etc.), which shall be discussed within this paper.

With today’s continuously increasing demand for flexibility in heavy duty gas turbines operation, power plant owners are forced to change their operation regime from base load to cyclic operation. The required coating properties for the two regimes are contradicting and cannot be optimized with current MCrAlY systems. Furthermore, for each turbine component, as well as in individual part locations, the loading boundary conditions are differently weighted. For an overall optimized component protection it is therefore of interest to produce coatings with flexible and individually tailored properties. In this context, ALSTOM invested into the development of an Advanced Modular Coating Technology (AMCOTEC), which is based on several powder constituents and a new application method, allowing in-situ compositional changes. With this approach, coating properties, such as oxidation, corrosion, erosion resistance, cyclic lifetime etc. can be modularly adjusted for individual component types and areas. This also includes production of functionally graded coatings, without changing the chemistry of powder fractions.