Mechanical and tribological properties of WO2.9 and ZrO2 + WO2.9 composites studied by nanoindentation and reciprocating wear tests

Abstract Oxygen vacancies in WO2.9 yield to formation of easy shear planes and they can potentially be applied in boundary lubrication conditions for reducing friction. Mechanical and tribological properties of pulsed electric current sintered monolithic WO2.9 were studied by nanoindentation and nanoscratch, and the composites of ZrO2 + WO2.9 with reciprocating wear tests. Hardness of WO2.9 at 25 °C was ∼11 GPa and reduced elastic modulus was ∼150 GPa. The ploughing dominated coefficient of friction as between 0.09 and 0.24 when measured against a Berkovich diamond tip. The composite n-ZrO2 + 10 vol% WO2.9 presented the lowest CoF, and wear rate 10−10 mm3/Nm measured under 10 N load against alumina ball (6 mm diameter) due to WO2.9 acting as a solid lubricant.