Study on wear behaviours for NBR/stainless steel under sand water-lubricated conditions

Abstract

Nitrile Butadiene Rubber (NBR) is widely used to make ship water-lubricated rubber stern tube bearings for marine applications. The sand in water is an important factor that affects the tribological properties of the rubber stern tube bearings. This study aimed to investigate the wear behaviours of NBR pins and 1Cr18Ni9Ti stainless steel disc rubbing pairs under sand water-lubricated conditions. A CBZ-1 tribo-tester was used to conduct sliding wear tests under the sand and pure water-lubricated conditions. The friction coefficients, wear volumes and different mass concentrations of sand were measured and compared. In addition, their surface morphologies were examined using optical microscopy and laser-interference profilometry. The results showed that the sliding velocity, applied load and mass concentration of sand had significant effects on the tribological properties of the rubbing pairs. The wear volumes and surface roughness of the rubbing pairs increased as the sliding velocity, applied load and mass concentration of sand increased. The friction coefficient also increased with the increase of applied load and mass concentration of sand, while it became smaller firstly and then bigger as the velocity increased. The sand particles destroyed the water-film between the rubbing pairs to reduce their tribological properties, and the abrasive wear was the main wear mechanism under the sand water-lubricated conditions. The data gained herein provides a better insight in to the wear process of NBR/1Cr18Ni9Ti stainless steel discs, and will be useful for selecting proper operating conditions for water-lubricated rubber stern tube bearings and will ensure the completion of missions by ships, reliably and safely.