New Methods of Evaluating Lubricants Based on the Surface Energy/Hardness Ratio 630435
Recent studies have shown that an important property of a contacting pair of materials, which determines their performance under sliding conditions, is the W/p ratio, where W is the energy of adhesion of the contacting surfaces, and p the penetration hardness of the softer of them. Associated with low W/p ratios are such properties as low friction and low wear, while high W/p ratios lead to severe surface damage and, in many cases, galling.
It has been found that the W/p ratio correlates well with two phenomena which accompany sliding, namely size of the wear particles, and the roughness induced in the surfaces. It is suggested that these phenomena, and especially the roughening effect, provide a very good indication of the nature of the sliding conditions. In addition, the measurement of equilibrium roughness values attained during lubricated sliding gives useful information to designers, as it suggests suitable values for the initial roughness and the clearance of contracting members of sliding systems.