Effect of holding time on microstructure and properties of dense alpha-Si3N4/Sialon composite coating on porous Si3N4 ceramic

摘要

A dense alpha-Si3N4/Sialon composite coating was fabricated on porous Si3N4 ceramic using the liquid infiltration and filling method in order to improve mechanical properties and waterproof. The effect of holding time on microstructure, water absorption and mechanical properties of the coating was investigated in detail. The results showed that all the coatings mainly consisted of a dominant alpha-Si3N4 phase and minor O'-Sialon, beta-Sialon and Y-Si-Al-O-N glass phase. The content of O'-Sialon phase increased gradually as the holding time increased from 0 to 3 h, however it started to decrease while the content of beta-Sialon phase increased abruptly when the holding time reached 4 h. As-prepared coatings exhibited good waterproof ability, and water absorption of porous Si3N4 ceramic decreased obviously after fabricating the coatings. Vickers hardness and fracture toughness of the coated porous Si3N4 ceramic increased gradually as the holding time increased from 0 to 3 h, but they decreased obviously when the holding time was 4 h because large amount of pores were formed within the coating. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.