Effect of alloy materials on properties of cermets
The addition amount of C has a great effect on the microstructure and properties of cermets. Too little C content in the organization will appear ɳ relative performance is harmful, but too much C content in the organization, there will be a free graphite, the same degrade the performance of the material. At the same time, the amount of C content can also control the dissolved amount of W and Ti in the binder.
Adding WC to cermet can improve wettability and sinterability. It has also been reported that introducing WC into Ti(C,N)-Ni system can increase toughness and inhibit grain growth rate.
The addition of Mo or Mo2C can significantly improve the wettability of Ni to TiC. Mo2C exists in the coating layer of the hard phase, which avoids the direct contact and aggregation of the hard phase and thus refine the grain. Meanwhile, the increase of Mo content in a certain range can improve the fracture toughness of the material.
The effect of Ni content on TiC-Ni-Mo cermets is similar to that of Co on WC-Co alloys. The flexural strength of cermets increases with the increase of Ni content, but the hardness decreases. In the literature, the effects of different Ni/Co ratios on the properties of materials were investigated under the condition that the total amount of binder phase was not maintained. The results show that the bending strength decreases with the decrease of Ni/Co ratio while the hardness increases.
Adding TiN to TiC-Mo-Ni cermets can obviously refine the hard phase particles, and improve the wear resistance, oxidation resistance and thermal conductivity of the materials. However, when the addition of TiN exceeds a certain degree, the hard coating layer of the material will become thin, and some coating layers will become incomplete, and free TiN will appear, which leads to the decline of comprehensive mechanical properties.
The addition of TAC and NbC can improve the discontinuous cutting performance of cermet tools, while the effect of Vc is to inhibit the grain growth. However, their addition will reduce the wettability of the bond relative to TiC, resulting in the decrease of the strength of the material.
In addition, proper addition of rare earth elements can purify the interface, refine the hard phase particles of Ti(C,N) -based ceramics, and improve the density, bending strength, hardness and fracture toughness of the materials.