Preparation and thermal shock behavior at 1000 °C of a glass-alumina-NiCrAlY tri-composite coating on K38G superalloy

Dense and well-adherent glass-alumina-NiCrAlY tri-composite coatings were prepared on K38G superalloy substrates at 950 °C. Their thermal shock resistance at 1000 °C was investigated, and compared with two glass-alumina composite coatings. Results indicated that the tri-composite coatings exhibited the best resistance to thermal shock and provided enough protective effect to the substrates from high temperature oxidation. The inclusion of alumina particles and NiCrAlY alloy platelets increased the indentation toughness and thermal expansion coefficient, accounting for the enhancement of thermal shock resistance of the tri-composite coatings. Oxidation of the superalloy substrates, combined with their interaction with glassy coatings, was also discussed.