Fabrication of dense β-Si 3 N 4 -based ceramic coating on porous Si 3 N 4 ceramic

β-Si3N4-based coating was prepared on the porous Si3N4 ceramic using the liquid infiltration and filling method. The effect of sintering temperature on microstructures, water absorption, mechanical properties and erosion resistance of the coatings were investigated. The results show that phase components of all the coatings consisted of β-Si3N4, Y10Al2Si3O18N4 and Y–Si–Al–O glass. The coatings prepared at 1700 and 1800°C had a good water resistance, which can be attributed to the high density of the coatings. The defects, including large pores and micropores, were produced within the coating when the sintering temperature was up to 1900°C, thus leading to the reduction of the water resistance. Hardness and elastic modulus of the coating increased gradually as the sintering temperature increased from 1700 to 1800°C, but it began to decrease when the sintering temperature was 1900°C. The coating prepared at 1800°C displayed a good erosion resistance.