Interfacial reaction between SiO2–Al2O3–ZnO–CaO based glass coatings and K38G superalloy substrates

In order to extend the use of a SiO2–Al2O3–ZnO–CaO based glass coating for higher temperature applications on Ni-base superalloy substrates, its interfacial reaction with the K38G superalloy substrates at 1000 °C was investigated. Results indicated that the interfacial reaction resulted in bubbling of the glass coatings due to Zn gas volatilization and formation of a loose TiO2 interlayer which finally accounted for the peeling of the coatings. With a pre-crystallization process of the glasses, its interfacial reaction was controlled and the bubbling of the coatings was avoided. After the heat-treatment at 1000 °C for 20 h, the glass coatings were still very dense and bonded well to the K38G superalloy substrates. Instead of a loose TiO2 interlayer, an Al-riched layer formed at the interfaces.