Study of CuO admixtures as antiwear additive in Machine Grease – 2

A low cost Machine Grease−2 has too poor anti-seizure properties to be used for lubrication of rolling bearings. To enhance its anti-seizure properties, a mixture of copper oxide, glycerol and ethyl alcohol was introduced into its volume in different proportions and examined using a four-ball tester. The aim of the study was to provide an answer to the question whether the copper oxide, in the mixtures proposed above, would undergo reduction to metallic copper to act as a solid lubricant in Machine Grease−2. These AES and XPS analyses showed the presence of metallic copper in the adlayer formed on the surface of tested balls, which resulted in a three- or fourfold increase in seizure resistance in comparison with pure Machine Grease−2. This confirms that, under the conditions of friction in the tester, copper oxide reduces to metallic copper which works as a solid lubricant.