Effect of Y2O3 additive on properties of cBN composites with Si3N4–Al2O3–Al as binder by high temperature and high pressure sintering

Abstract

Abstract In this study, cBN composite was prepared by high temperature high pressure (HTHP) sintering using Si3N4, Al2O3 and Al as main binders. Effects of Y2O3 addition on thermal and mechanical properties of cBN composites were systematically evaluated. The results show that a eutectic melt Y–Si–Al–O–N was formed in composites with the addition of Y2O3 under HPHT sintering process, and the presence and quantity of eutectic liquid accelerated the densification of composites. Mechanical properties of cBN composites by incorporating Y2O3 fillers had an obvious improvement. The composite incorporating 2 wt% Y2O3 at 1550 °C presented outstanding relative density of 99.38%, high bending strength of 610.5 MPa, superior hardness of 49.2 GPa and oxidation temperature of 1215.9 °C, while 5 wt% Y2O3 doped composite exhibited the max fracture toughness of 7.2 MPa⋅m1/2. Overall, cBN composites look promising for future use in cutting inserts due to their improved mechanical properties and thermal performances.