Wear Behavior of (TiB2–TiC)–Ni/TiAl/Ti Gradient Materials Prepared by the FAPAS Process
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(TiB2–TiC)–Ni/TiAl/Ti functionally gradient materials were prepared by field-activated pressure-assisted synthesis processes. (TiB2–TiC)–Ni composite ceramic, the top layer of the functional gradient materials, was prepared in situ by the combustion synthesis process using Ti and B4C powders as raw materials. Scanning electron microscope (SEM) images of the ceramic layer revealed that the TiB2 and TiC particles in the composite were fine and homogeneously dispersed in the Ni matrix. The friction and wear properties of the (TiB2–TiC)–Ni ceramic were evaluated by sliding against a GCr15 disk at temperatures from ambient up to 400 °C. The experimental results showed that the friction coefficient of the (TiB2–TiC)–Ni ceramic decreased with the increasing testing temperature, load, and sliding speed. However, the loss rate decreased at higher temperature and increased at higher load and higher sliding speed. The wear mechanisms of (TiB2–TiC)–Ni ceramic mainly depend upon thermal oxidation at higher temperature, load, and sliding speed. The worn topography and phase component of the worn surfaces were analyzed using SEM, energy dispersive spectroscopy, and X-ray diffraction. The oxide films of Fe2O3, TiO2, and B2O3 formed during the friction process play an important role in lubrication, which results in a smaller friction coefficient.
KeywordsBorides Carbides Friction mechanisms Self lubrication friction Ceramic composite
This study was supported by projects of the National Science Foundation of China (No. 50975190), Shanxi Province Science Foundation for Youth and Young Scientists Fund of the National Natural Science Foundation of China (51101111).
Conflict of interest
The study has been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki. All the authors agree to submit the paper to Tribology Letters.