EFFECT OF WATER AND N-ALCOHOLS ON THE TRIBOLOGICAL PROPERTIES OF A CHROMIUM-OXIDE COATING

The tribological properties of self-mated plasma-sprayed Cr2O3 coating s were studied with a block-on-ring machine at room temperature using distilled water, water-ethanol, n-monohydric alcohols and polyhydric a lcohols as lubricants. Testing results indicated that both friction an d wear were much higher in water than in the n-monohydric alcohols. Th e friction coefficient was 0.27 in water, and 0.07 to 0.13 in the n-al cohols. Wear in water was at least twice as high as that in n-alcohols . The friction and wear decreased slightly with an increase in the cha in length. In ethanol, friction and wear increased rapidly when a smal l amount Of water was blended into the lubricant. In the polyhydric al cohols, the increase of the hydroxyl number greatly decreased friction and wear. The analyses of morphology and composition of the worn surf aces indicated that the wear of Cr2O3 coating was controlled by the co mbination of microfracture and tribochemical wear in water and is cont rolled by microfracture wear in ethanol.