On the stability of amorphous silica coatings for high-temperature service

Amorphous silica coatings significantly improve the resistance of Incoloy 800H to attack in aggressive atmospheres at temperatures up to 1000 °C. Eventually, however, failure occurs due to crystallisation of the silica and solid-solid interactions between the coating and substrate. Crystalline silica nucleated beneath a layer of alloy, which had been depleted in chromium on forming a pre-coating oxide layer. Due to the difference in chemical …