Performance improvement of Si3N4 ceramic cutting tools by tailoring of phase composition and microstructure

Abstract Silicon nitride (Si3N4) ceramic cutting tool with excellent cutting performance was successfully achieved through the control of phase composition and microstructure. The hardness of the tool with 49.7 wt% and 4.9 wt% α-Si3N4 is ∼20.1 GPa and ∼17.5 GPa, respectively. In continuous cutting of cast iron, the tool life significantly increases from ∼1200 m to ∼2400 m when α-Si3N4 content increases from 4.9 wt% to 49.7 wt%, respectively. The longer tool life is attributed to a better abrasive and adhesive wear resistance of α-Si3N4 phase. In addition, the chemical reaction between Si3N4 ceramic tool and cast iron would lead to the formation of an amorphous oxide layer on wear surface. It was noted that the higher α-Si3N4 content would lead to greater probability of chipping due to lower fracture toughness. Therefore, high-performance Si3N4 ceramic tool could be achieved using an α-Si3N4 matrix ceramic reinforced with elongated β-Si3N4 phase.