Fabrication and thermal shock resistance of β-Si3N4-based environmental barrier coating on porous Si3N4 ceramic

Abstract

A dense β-Si3N4-based waterproof environmental barrier coating was fabricated using the liquid infiltration and filling method on porous Si3N4 ceramic. Microstructure and thermal shock resistance of the coating were investigated. The results showed that the coating consisted of β-Si3N4, Y10Al2Si3O18N4 and Y-Si-Al-O glass. As-prepared coating exhibited excellent thermal shock resistance. During thermal shock at ∆T=1200°C, cracks were formed within the coating, but they did not penetrate through the whole coating due to the toughening mechanisms of the coating, including β-Si3N4 particle bridging and crack branching. In addition, the coating had a good crack self-sealing ability during thermal cycling, which is mainly attributed to glass flow and oxidation of β-Si3N4 particles within the crack. After thermal cycling for 25 times, the coating still had a good waterproof ability, and the water absorption of the coated porous Si3N4 sample increased slightly from 4.5% to 9.3%.