Tribological properties of NbTiTa self-lubricating medium-entropy composites over a wide temperature range

The mechanical and structural stability of refractory high-entropy or medium-entropy alloys at high temperatures provides new directions for the development of high-performance self-lubricating materials. In this study, NbTiTa-Ag-BaF2/CaF2 self-lubricating composites were successfully prepared using powder metallurgy technology, and their friction and wear behaviors over a wide temperature range were investigated. The self-lubricating composites exhibit low and stable COF values at the tested temperatures compared to NbTiTa alloy, with the average COF ranging from 0.29 to 0.44. Meanwhile, the presence of solid lubricants effectively reduces the wear rates of NbTiTa alloy at RT, 400 °C, and 800 °C, but the appearance of cracks and spall pits increases the wear at 600 °C. •NbTiTa-Ag-BaF2/CaF2 self-lubricating composites were made via powder metallurgy.•The composites show low and stable COF values at temperature from 25 °C to 800 °C.•Solid lubricants reduce wear rates of NbTiTa alloys at 25 °C, 400 °C, and 800 °C.