Microwave synthesis of duplex α/β-SiAlON ceramic cutting inserts: Modifying m, n, zvalues, synthesis temperature, and excess Y2O3synthesis additive

Duplex α/β-SiAlON ceramic cutting inserts (30α:70β) were synthesized by microwave sintering. The effects of solid solution parameters (m, n, z), synthesis temperature, and amount of excess Y2O3synthesis additive on phase assemblage, microstructure, mechanical properties, and cutting performance were systematically investigated. It was found that increasing mvalue could improve the formation of α phase while high zvalue over 1.0 resulted in the dissolution of α phase into β phase and intergranular phase. Increasing the amount of excess Y2O3could promote densification and elongated β grain growth; however, the excess Y2O3amount above 4 wt% resulted in substantial crystallization of M’SSphase, thus declining the mechanical properties and wear resistance. The microwave-synthesized α/β-SiAlON cutting insert with modified parameters (m= 1.7, n= 1.0, z= 0.7, and 3 wt% excess Y2O3) was obtained with optimal comprehensive properties, whose tool life was found to increase by approximately 75% in high-speed milling of Inconel 718 superalloy compared to the commercial α/β-SiAlON cutting insert.