An efficient lubrication condition based on the difference of material wettability

Materials with different wettabilities and with two different roughness intervals, Ra (0.003-0.08) and Ra (0.08-3), were taken into consideration. In particular the following material are tested: AISI 420, AISI 1050, AISI 316L, PH14-7, CoCr alloy, PTFE, UHMWPE, Peek 450G, Peek CA, Peek CF, Torlon 4203L, Rexolite 1422, Pyrex Glass, and others. The wear tests, in dry and water lubrication, have been performed with a Pin on Disk tribometer (ASTM 99G norm) with continuous drop addition system in air environment. The wettability of each material was measured using the model of the contact angle θ. The wettability difference (Δθ) for every tribological coupling taken into consideration, was calculated. From obtained results it's easy to note that the friction coefficient, the wear, the width track and the analysis at scanning electron microscopy (SEM), evidence their agreement with the trend of the difference of wettability (Δθ) between the two coupling materials, in fact the best tribologic behaviour occurs when the Δθ assumes its highest values. The more higher it's the difference of wettability (Δθ) between coupling materials, the more efficient it's the lubricant condition, i.e. a stable supporting “meatus “ is formed. All the tests lead to the conclusion that the materials in tribological coupling, must be rigorously selected taking into consideration the interaction among the difference of wettability of the materials in coupling and their mechanical characteristics.