Composition for boundary lubricant and method

Abstract

A composition for forming a boundary lubricant for metal and ceramic wear surfaces consisting of transition element complexes, including those of the higher molecular weight carboxylic acids such as the long chain fatty acids (C.sub.x H.sub.2x.sub.+1 COOH; x = 8, 9, 10, . . . 29). The transition elements used here are metals such as Cr, Mn, Fe, Co, Ni or Al that can form coordination complexes. Exemplary metal complexes are chromium stearate and chromium behenate. An exemplary complex may be prepared by (1) reducing chromium trioxide by a reducing alcohol in a low molecular weight organic acid to produce chromium acetate; then 2 hydrating and olating the chromium acetate. A solution containing a maximum concentration of about 11 weight percent of the transition metal complex in a solvent such as trichloroethylene is applied as a thin layer onto a wear surface, then the layer is heated for 1-4 hours at a temperature at or above 70.degree.C and, within the approximate range 70.degree.-160.degree.C. The transition metal complex chemically adheres to the wear surface, and is cross-linked by the heat treatment, to form an anchored, polymerized array of molecules that provides a hydrophobic, durable, boundary lubricant having a low coefficient of friction. The transition metal complex solution may be applied to non-porous wear surfaces or, alternatively, may be impregnated into chrome oxide coatings or other porous refractory coatings on wear surfaces to form a porosity-filling boundary lubricant thereon. The lubricant decreases the clearance required between porous bearing surfaces, decreases the formation of corrosion cells, and lowers the coefficient of friction. The preferred amount of fatty acid or organic polyacid that can be stably incorporated into a complex chromium soap for use as a porosity-filling lubricant, that is, the optimum fatty acid mol/chromium gm-atom ratio, is approximately 1-1.2/1.