Microwave sinteringof duplex α/β-SiAlON ceramic cutting inserts: modifying m, n, z values, sintering temperature and excess Y2O3 sintering additive

Duplex α/β-SiAlON ceramic cutting inserts (30α: 70β) were fabricated by microwave sintering. The effects of solid solution parameters ( m , n , z ), sintering temperature and amount of excess Y 2 O 3 sintering additive on phase assemblage, microstructure, mechanical properties and cutting performance were investigated. It was found that increasing m value could improve the formation of α phase while high z value over 1.0 would lead to the dissolution of α phase into β phase and intergranular phase. Increasing amount of excess Y 2 O 3 could promote densification and elongated β grain growth, but the excess Y 2 O 3 over 4 wt.% would result in substantial crystallization of M' SS phase thus declining the mechanical properties and wear resistance. The microwave-sintered α/β-SiAlON cutting insert with modified parameters ( m  = 1.7, n  = 1.0, z  = 0.7 and 3 wt.% excess Y 2 O 3 ) was obtained with optimal comprehensive properties, whose tool life was increased by approximately 75% in high-speed milling of Inconel718 superalloy as compared with commercial α/β-SiAlON cutting insert.