Changes in Microstructure of Air Plasma Sprayed MCrAlY Coatings After Short Thermal Exposure in Argon Atmosphere

Changes in Microstructure of Air Plasma Sprayed MCrAlY Coatings After Short Thermal Exposure in Argon Atmosphere

journal article - other

en

Two NiCrAlY and CoNiCrAlY powders were used to produce the MCrAlY type of coatings by means of conventional thermal air plasma spraying on Inconel 713LC nickel-based superalloy substrate. After spraying, an initial state of both types of coatings consisted of the beta-NiAl intermediate phase, gamma-Ni solid solution and it also included a certain amount of imperfectly melted powder particles, voids and Al2O3 oxide particles. The coatings were annealed for two hours at wide range of the temperatures (650, 800, 1000 and 1150oC) in argon-flow atmosphere. After this short thermal exposure the changes in the microstructures were studied in detail. It was found that the temperature influences the coatings microstructure significantly. On the other hand, it has only minor effect on the coatings thickness, which is almost equal to its initial state value. At high temperatures, the oxide scale is formed by internal oxidation being the most detrimental mechanism. In the consequence, the beta-NiAl intermediate phase disappears and the gamma-Ni, alpha-Cr solid solutions and Al2O3 oxide starts to form within the coatings. No interaction at the coatings-substrate interfaces were observed after this short thermal exposure. The coatings' microstructure was studied by scanning electron microscope. Layer thickness and the amount of the oxide scale in coatings were measured by means of image analyses. Chemical composition was estimated by energy dispersive microanalysis measurements.

Two NiCrAlY and CoNiCrAlY powders were used to produce the MCrAlY type of coatings by means of conventional thermal air plasma spraying on Inconel 713LC nickel-based superalloy substrate. After spraying, an initial state of both types of coatings consisted of the beta-NiAl intermediate phase, gamma-Ni solid solution and it also included a certain amount of imperfectly melted powder particles, voids and Al2O3 oxide particles. The coatings were annealed for two hours at wide range of the temperatures (650, 800, 1000 and 1150oC) in argon-flow atmosphere. After this short thermal exposure the changes in the microstructures were studied in detail. It was found that the temperature influences the coatings microstructure significantly. On the other hand, it has only minor effect on the coatings thickness, which is almost equal to its initial state value. At high temperatures, the oxide scale is formed by internal oxidation being the most detrimental mechanism. In the consequence, the beta-NiAl intermediate phase disappears and the gamma-Ni, alpha-Cr solid solutions and Al2O3 oxide starts to form within the coatings. No interaction at the coatings-substrate interfaces were observed after this short thermal exposure. The coatings' microstructure was studied by scanning electron microscope. Layer thickness and the amount of the oxide scale in coatings were measured by means of image analyses. Chemical composition was estimated by energy dispersive microanalysis measurements.

Two NiCrAlY and CoNiCrAlY powders were used to produce the MCrAlY type of coatings by means of conventional thermal air plasma spraying on Inconel 713LC nickel-based superalloy substrate. After spraying, an initial state of both types of coatings consisted of the beta-NiAl intermediate phase, gamma-Ni solid solution and it also included a certain amount of imperfectly melted powder particles, voids and Al2O3 oxide particles. The coatings were annealed for two hours at wide range of the temperatures (650, 800, 1000 and 1150oC) in argon-flow atmosphere. After this short thermal exposure the changes in the microstructures were studied in detail. It was found that the temperature influences the coatings microstructure significantly. On the other hand, it has only minor effect on the coatings thickness, which is almost equal to its initial state value. At high temperatures, the oxide scale is formed by internal oxidation being the most detrimental mechanism. In the consequence, the beta-NiAl intermediate phase disappears and the gamma-Ni, alpha-Cr solid solutions and Al2O3 oxide starts to form within the coatings. No interaction at the coatings-substrate interfaces were observed after this short thermal exposure. The coatings' microstructure was studied by scanning electron microscope. Layer thickness and the amount of the oxide scale in coatings were measured by means of image analyses. Chemical composition was estimated by energy dispersive microanalysis measurements.

difuze, Inconel 713LC, NiCrAlY, CoNiCrAlY, niklové aluminidy

diffusion, Inconel 713LC, NiCrAlY, CoNiCrAlY, Nickel-aluminide

2011

06.08.2011

POLISH ACADEMY OF SCIENCES INSTITUTE OF PHYSICS

Warsaw, Poland

0587-4246

120

2

336–339

4