Investigating the Micropitting and Wear Performance of Copper Oxide and Tungsten Carbide Nanofluids under Boundary Lubrication
The potential of copper oxide (CuO) and tungsten carbide (WC) nanofluids in enhancing micropitting and wear behavior of AISI 8620 steel under boundary lubrication conditions was investigated. The nanofluids consisted of 1% nanoparticles by weight and 1% by weight of oleic acid surfactant in Polyalphaolefin (PAO). Rolling contact fatigue tests were conducted using a micropitting test rig (MPR). Both the nanofluids exhibited increased micropitting life compared to the base oil. Tungsten carbide nanofluids showed significantly higher micropitting and wear resistance behavior than the CuO nanofluids under the boundary lubrication regime. Analysis of the surfaces showed different mechanisms to inhibit micropitting and wear for the two nanofluids. The WC nanofluid formed a tribofilm whereas the CuO nanofluids tended to fill surface cracks with the nanoparticles.