Quality improvement of chrome-calorizing coatings, obtained with gas-circulating

In this paper we examine chrome-calorizing coatings obtained with the gas-circulating method. They are widely used for protecting the interior cavity of working blades in modern gas-turbine engines. The findings of the research illustrate that the alloy composition and residual air pressure in the installation have an essential influence on operational properties and coatings quality. We determined the conditions of combined chrome and aluminium mass transfer to the surface of the component. Consequently, it became possible to replace the two-stage consistent elements precipitation with the more economical one-stage process. Within the research we found out, that residual air pressure in the installation before the saturation process has an effect on the quantity of oxide Al₂O₃ particles in the coatings. By means of computer simulation, we analyzed the effect that the particles, their size and form have on the thermal stress in the exploitation process of the cooled blades. Moreover, by thermodynamic calculations, we substantiated and experimentally confirmed the possibility of a complete prevention of forming aluminum oxide in the coating in case of using nickel yttrium alloys.

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