High performance environmental barrier coatings, Part II: Active filler loaded SiOC system for superalloys

Polymer derived ceramic (PDC) matrix composite coatings are a promising candidate to be used as alternative environmental barrier coatings, such as in oxidation protection. This paper reports the processing of three PDC coating systems on a superalloy substrate, Inconel 617, using a simple dip coating method. The performance of SiON coating, particle filled SiOC coating, and their combined coating system is evaluated by long time static oxidation testing at 800 °C for 100–200 h. Two key parameters have been analyzed: the weight gain of the coating samples and the thickness of the thermally grown oxide (TGO) layer at the ceramic–metal interface. Results show that all three coating systems are able to significantly reduce the weight gain of metal substrates due to oxidation. However, the SiON bond coat + particle filled SiOC top coat double-layer coating system is most effective in maintaining the integrity of the substrate in the investigated 200 h. Based on the kinetics of oxidation, likely rate controlling steps are identified.

► Environmental barrier coatings made from polymer derived ceramics.
► Long-term static oxidation testing (100 and 200 h at 800 °C in air).
► Outstanding oxidation resistance of the double-layer ceramic matrix composite coating system.
► Coating weight gain and TGO thickness growth revealed the failure mechanisms of three different systems.