Tribo-physical and tribo-chemical aspects of WC-based cermet/Ti3SiC2 tribo-pair at elevated temperatures

The tribological behaviors of tungsten carbide (WC) based cermet/Ti₃SiC₂ tribo-pair at elevated temperatures were investigated. Lead oxide (PbO) was added as a solid lubricant. The tribo-physical and tribo-chemical changes on sliding surfaces were studied in detail. The results indicated that adhesive and abrasive wear due to removal of metallic binder and pullout of grains were the dominant wear mechanisms at room temperature. At high temperature, tribo-physical changes (i.e. mechanical mixture or sintering) and tribo-chemical reactions including complex reaction and oxidations were induced by frictional heat combined with high environmental temperature. As a result PbWO₄ was formed as a reaction product and acted as a solid lubricant. PbWO₄ and tribo-oxides along with the physically changed layer on the sliding surfaces were favorable to reduce wear of both materials. At high temperature, the wear mechanism varied from adhesive and abrasive wear at room temperature to lubrication by tribo-layer containing PbWO₄, tribo-oxides, and sinters at high temperatures.