Investigation of thermal phase evolution in Cr2(C,N) inhibitor for optimizing high-performance cemented carbide sintering process

Abstract

The introduction of inhibitors containing nitrogen has demonstrated its efficacy in the fabrication of high-performance cemented carbides. Nevertheless, the thermal instability of nitrogen-doped compounds also presents a heightened risk of nitrogen removal, which can adversely affect the density of the carbides. Hence, this study aimed to explore the thermal stability of a widely employed nitrogen-containing Cr2(C,N) inhibitor. The findings reveal that a well-established denitrification process commences at 950 °C and intensifies above 1200 °C, accompanied by a Cr2(C,N) → Cr7C3 → Cr23C6 phase evolution. Utilizing the aforementioned insights, the sintering process was optimized by adding an isothermal treatment to obtain dense and refined cemented carbide exhibiting high performance. As a result, the sintered ultrafine WC-10Co alloy maintains a series of excellent comprehensive performances combined with high transverse rupture strength (4850 MPa), high fracture toughness (10.6 MPa·m1/2), and high hardness (1870 kg/mm2). This work provides basic guidance on sintering strategy design for preparing high quality cemented carbides with nitrogen-contained inhibitors.