Effects of yttrium and cerium additives in lubricants on corrosive wear of stainless steel 304 and Al alloy 6061

Effects of oxygen active elements, yttrium and cerium, as additives in commercial lubricants on corrosive wear were investigated. Sliding wear losses of stainless steel 304 and Al alloy 6061 lubricated by oil and thin grease respectively with and without yttrium or cerium additive in a corrosive environment were determined. Dilute H₂SO₄ solution (10% H₂SO₄) was used as the corrosive medium and added to the lubricants for the corrosive wear test. The wear test was performed on a pin-on-disc tribometer with the capability of measuring wear in lubricant. The disc was coiled with a copper tube, through which cooling water could pass, so that the wear losses respectively under cooling condition and non-cooling condition could be determined. The results showed that wear losses of the tested materials caused by synergistic attack of wear and corrosion can be effectively reduced by adding small amounts of yttrium or cerium to the lubricant. In addition, the effect of the additives was found more distinctive under the non-cooling condition. Worn surfaces were examined using SEM to clarify the wear mode and thus the wear mechanism.