Passive filler loaded polysilazane‐derived glass/ceramic coating system applied to AISI 441 stainless steel, part 1: Processing and characterization

This study describes an oxidation and corrosion resistant environmental barrier coating (EBC) applied to an AISI 441 stainless steel substrate. For this purpose, four polymer‐derived ceramic (PDC) coating systems were developed. These coating systems consisted of a bond coat applied by dip coating, and a top‐coat that was loaded with passive fillers and deposited by spray coating. The microstructures of the coatings were investigated using optical microscopy and scanning electron microscopy, including energy dispersive spectroscopy (EDS). X‐ray powder diffraction (XRD) was used to investigate the phase composition of the coatings. The optimized composite top coatings were prepared from the preceramic polymer HTT1800, filled with yttria‐stabilized zirconia and a specially tailored Al2O3–Y2O3–ZrO2 (AYZ) passive filler, and commercial barium silicate glasses were used as sealing agents. After thermal treatment in air at 750°C, uniform and crack‐free composite coatings on stainless steel substrates were developed, with thicknesses of up to 93 μm. Oxidation tests, which were performed at 850°C in synthetic air, showed that every tested coating system remained undamaged by oxidation and showed good bonding to the metal substrate.