Oxidation behaviors of SiOCN coatings with tunable carbon content on stainless steel at 800 °C in Ar, Ar + H2O, and air atmospheres

Abstract

This work investigates the influence of carbon content on the thermal stability of SiOCN coatings derived from polysilazanes on AISI 304 stainless steel after 100 h exposure at 800 °C to Ar, Ar + H₂O, and air. Two polysilazanes with different ratios, including carbon-free (perhydropolysilazane, PHPS, (P)) and carbon-rich (Durazane 1800 (D)), were used as the coating materials. The carbon-free (P) coating exhibited superior oxidation resistance, forming a protective SiON layer. In contrast, the carbon-rich coating (D) resulted in duplex oxide nodules, indicating breakaway oxidation. The coatings with intermediate carbon contents showed a mixed behavior; areas with intact coatings adhered well to the substrate and provided significant protection, while localized spallation exposed the substrate to oxidation. The study highlights how PHPS and Durazane 1800 mixtures alter the precursor's behavior during pyrolysis and thermal treatment at 800 °C. These findings provide insight into the design of polymer-derived ceramic coatings for structural components in harsh environments such as power generation and aerospace.