Friction and wear of Ni alloy-Ag-Ni doped hBN self-lubricating composites from room temperature to 800 °C

Abstract

Abstract The current investigation explores the potential of Ni doped hBN (hBN-O-Ni) as a solid lubricant in conjunction with Ag in affecting the tribological performance of Ni alloy-Ag- hBN composites containing a fixed amount of silver (10 wt.%) and different amounts (2, 4, 6 and 8 wt.%) of hBN from room temperature to 800 °C by carrying out tests under a fixed load of 5N and speed of 0.5 m/s using a ball-on-disk tribometer. The study also intends to determine the optimum content of addition of hBN requited to attain low friction and low wear properties over the entire range of temperature. The composite having 8 wt. % hBN has shown the lowest coefficient of friction (~ 0.18) at 800 °C due to synergetic action between silver molybdates and hBN. However, the composite containing 4 wt. % hBN has the optimum tribological properties under the conditions used in the present study. At low temperatures, Ag and hBN provided lubrication, whereas at high temperatures lubricious oxides (NiO, NiMoO4 and MoO3), silver molybdates (Ag2MoO4, Ag2Mo2O7) and hBN contributed to lowering the coefficient of friction as well as wear rate.