A Study of the Effects of Unconventional Lubricants on the Wear Mechanisms of Shaft and Journal Bearings.

When handling fluids with unknown lubricating properties, pumps often work under unbalanced geometric parameters, radial loads and sliding speeds, ogether with inadequate material selection. These circumstances shorten the lifespan of shafts and bearings, which is often exacerbated when fluids exhibit non-Newtonian behaviour, or contain suspended abrasive particles. The resulting unplanned obsolescence potentially affects a large share of the European Industrial Original Equipment Manufacturers, and is considered a relevant and unsolved environmental issue. In relation to transporting fluids of the food and beverage and chemical industries, the present study assesses this issue aiming at two scientific goals: the development of a predictive model identifying mixed lubricating regime conditions, and the analysis of wear and corrosion resistance performance of a set of steels subjected to surface treatments or functional metallic coatings. A ball and disk contact configuration in a sliding-rolling mini-traction machine (PCS Instruments MTM2) has been adopted to experimentally test the friction performance and to generate Stribeck plots. Threshold conditions between hydrodynamic and mixed regimes have been analytically identified, and later correlated with roughness, applied load, entrainment speed, and mechanical properties of both contacting surfaces and the interstitial fluid, adopting Hamrock-Dowson elasto-hydrodynamic model. A potential predictive algorithm was therefore derived for linear contact in shaft and journal bearing geometry.