Thermal conductivity and oxidation behavior of porous Inconel 625 coating interface prepared by dual-injection plasma spraying

Plasma sprayed Inconel 625 coating with desired microstructures and porosity can be a potential gas transpiration interface between the hot and cold fluid medium in gas turbines while cooling the components through transpiration film-cooling technique. In scope of this work, we produced porous Inconel 625 coatings by using dual injection plasma spraying. Polyester powder was used as the pore former which was separately injected during the spraying of Inconel 625 powders at optimum spraying conditions. The sprayed coatings were subjected to heat treatment to remove the polyester and to create porosity in the coatings. Feeding conditions of external pore former were optimized to obtain the coatings with desired porosity levels (4 ± 2% to 48 ± 9%). Thermal conductivity of the Inconel 625 coatings with different porosity levels (4 ± 2%; 23 ± 3% and 34 ± 5%) were measured by laser flash method and were subjected to isothermal oxidation at 950 °C for 200 h to estimate their oxidation rates. Obtained results showed that the thermal conductivity of the coatings decreased and oxidation rate increased with respect to increase in the porosity level in the coating microstructures. [Display omitted] •Reliable porous coating by dual-injection plasma spraying•Controlled porosity in coating microstructure•Low thermally conductive porous Inconel 625 coating•Potential interface for gas transpiration film-cooling