Effect of La2O3 additions on microstructure and mechanical properties of Ti (C,N)-WC-Mo2C-Ni-Co cermets

作者：Qiu, Hao; Li, Xiao-qiang^*; Jiang, Chen-yang; Pan, Cun-liang; Qu, Sheng-guan

来源：Journal of Central South University, 2023, 30(6): 1751-1762.

DOI：10.1007/s11771-023-5362-0

• Ti(C
• N)-based cermets
• earth elements
• La2O3
• core-rim structure
• fracture toughness

Rare earth elements were considered alternative additives beneficial to the TiCN based cermets, but their effect with high content Mo2C has not been thoroughly investigated. In this study, Ti(C, N)-WC-Mo2C-Cr3C2-Ni-Co cermets containing 12 wt.% Mo2C doped with different contents of La2O3 were prepared by vacuum hot-press sintering at 1500 & DEG;C. Parametrical analysis on La2O3 addition (0, 0.5 wt.%, 1.0 wt.%, 1.5 wt.%, and 2.0 wt.%) was conducted, in terms of microstructure and mechanical properties of Ti(C, N) based cermets. Experimental results show that when the content of La2O3 increases from 0 to 1.0 wt.%, the ratio of core phase increases while the ratio of brittle rim phase decreases. Nanostructure is formed on the grain boundary of ceramic phase, which effectively inhibits the abnormal growth of rim structures. This can thin the brittle shell, coarsen the core phase, and refine the grains, thus improving its mechanical properties, including hardness and fracture toughness. When the addition amount of La2O3 increases from 1.5 wt.% to 2.0 wt.%, it will aggregate to form larger particles of about 100 nm, which sharply reduces its mechanical properties. The optimal La2O3 addition is 1.0 wt.%, in which Ti(C,N)-based cermets show the optimal comprehensive mechanical properties: the Vickers hardness and fracture toughness are 16.55 GPa and 6.14 MPa & BULL;m(1/2), respectively. This work provides further knowledge about the effect of rare earth on the core-rim structure and mechanical properties of Ti(C,N)-based cermets with high Mo2C contents.