The Relationship Between The Wettability And The Valence Electron Structure Of Ceramic Phase In Ti(C,N) Based Cermets

Owing to its combinations of high red-hardness, low friction coefficient, good wear resistance, excellent corrosion resistance and low cost, etc, Ti(C,N) based cermets is in a process of replacing the TiC based cermets and conventional WC-Co cemented carbides in cutting tool applications. However, in a long time, the toughness and resistance to impact are not satisfactory because metal Ni can't wet TiC and TiN completely, its applications are limited. In the paper, the relationship between the wettability and the valence electron structure of ceramic multiphase in Ti(C,N) based cermets was studied, which expects to present theoretical instruction for preparation of high performance cermets and enrich materials design theory.Firstly, the wettability of Ni on Ti(C,N) based ceramic multiphase was researched by sessile drop method. The results showed that the effects of the experimental conditions and the preparation of specimens on contact angle were obvious. The additions of carbides to Ti(C,N) solid solution could decrease contact angle of the system, the order was Mo2C>TaC>WC>VC>NbC, and the contact angle deceased continually with increasing the addition of other carbides or decreasing the ratio of TiC in ceramics phase. SEM/EDS characterization revealed that the improvement of the wettability was relative to the dissolution and diffusion of carbides in Ni, and reflected in microstructure of interfaces.Secondly, the bonding between Ni and ceramic were investigated through vacuum welding technique. The work of cohesion increased with the enhancement of wettability, but the bending strength of the welding specimens did not. When WC or Mo was added the mode was adhesive rapture (II) because of the difference between the thermal expansion coefficient of WC, Mo and Ni. The bending strength was high when IV rapture was occurred.Thirdly, the valence electron structure of ceramic multiphase in Ti(C,N) based cermets were calculated by EET theory, the results showed that nA increased with additions of carbides, the order was VC>Mo2C>NbC>WC>TaC. Based on the valence electron structure, the relationship between composition and wettability was set up through multiple linear and polynomial regressions.