[T15] Hard Materials

[16F-T15-02] Mechanical and Cutting Properties of New Ultrafine-Grained Cemented Carbide of WC-Ti(C,N)-Cr₃C₂-Co

*M. Takada¹, T. Tsutsumi^{1, 3}, Y. Mori¹, S. Terasaka^{2, 3}, H. Matsubara³ (1. Nippon Tokushu Goukin, Co., Ltd., Japan, 2.Japan Fine Ceramics Center, Japan, 3.Tohoku University, Japan)

Keywords:Cemented Carbide, ultrafine, grain growth, pinning effect, Ti(C,N)

The WC-Co ultrafine cemented carbides with addition of Ti(C,N) particles with different sizes were fabricated by liquid phase sintering. The microstructures of these alloys were investigated by comparing with various carbides. The fine Ti(C,N) addition inhibited the growth of WC grains, which was almost equal to that of Cr₃C₂ addition. The mechanism of the grain growth inhibition effect by adding Ti(C,N) particles was discovered to be the pinning effect (Zener) of the second phase particles, which was considered different from the conventionally reported mechanism of addition of VC and Cr₃C₂. The combined addition of Cr₃C₂ to this alloy resulted in extremely high strength, with the average strength of 4.7 GPa and the maximum strength of 5.1 GPa, the world’s highest level. When these materials were applied to a cutting tool, they demonstrated excellent cutting life; moreover, novel applications can be expected to take advantage of these characteristics.