WEAR-RESISTANT TICN-BASED CERAMIC MATERIALS FOR HIGH-LOAD FRICTION UNITS

Abstract

The tribological properties of titanium carbonitride composites of matrix and skeletal types were studied in dry friction conditions in air. Experiments on wetting of the TiN−Cr₃C₂ composite by nickel−chromium alloys and copper using the sessile drop method were performed to choose composition of the matrix and ascertain whether the samples could be produced by impregnation of the porous skeleton. The sessile drop experiments showed that nickel and its alloys formed a low contact angle on the TiСN–Cr₃C₂ composite (θ » 8°). In particular, Ni₃Al had θ < 5°, allowing it to be used as a metal matrix. The same situation was observed for copper. A technique was developed for producing TiN–Cr₃C₂ composites by impregnation of the porous skeleton by Ni₃Al and copper melts and the tribological behavior of the cermets was tested in dry friction conditions. When the starting composite was impregnated with Ni₃Al intermetallic, the friction coefficient decreased (µ = 0.25). Structural studies were conducted with a MIM-10 metallographic microscope and X-ray diffraction with a DRON-2 diffractometer. The hardness and contact area thickness were measured employing a Falcon 9 hardness tester (manufactured in the Netherlands). Thin cross sections were made to examine the structure and phase composition of the contact area. The structure was analyzed using X-ray diffraction and scanning electron microscopy. The effect exerted by hardness of the counterface (steel 45, 40Kh, ShKh-15) on the tribological properties of the TiСN–Cr₃C₂ composite was established. When steel hardness was 60 HRC, the friction coefficient increased with friction path. These results were, however, obtained at low speeds and loads. Friction losses decreased with loading increasing from 2 to 6 MPa at 12 m/sec: friction coefficient reduced to 0.23. The TiCN–20% Cr₃C₂ cermets impregnated with Ni₃Al may be recommended as antifriction materials for use in high-speed and high-load friction units.