Seizure Strength Improvement for Phosphate-Stearate Coatings Involved in Cold Forging of Steel

[+] Author and Article Information
Ph. Hivart, J. P. Bricout, J. Oudin

Laboratoire de Génie Mécanique, Unité de Recherche Associée au CNRS D1401, Mecamat Université de Valenciennes et du Hainaut Cambrésis, 59326 Valenciennes Cedex, France

J. Y. Dauphin

Laboratoire de Mécanique et Matériaux, Institut Industriel du Nord, 59651 Villeneuve d’Ascq Cedex, France

J. Tribol 114(2), 248-252 (Apr 01, 1992) (5 pages) doi:10.1115/1.2920880 History: Received June 10, 1991; Revised October 01, 1991; Online June 05, 2008


A seizure test particularly well suited to evaluate the mechanical strength of phosphate-stearate coatings has been developed. Test results, including tangential friction force and time at the onset of seizure, are related to the effective phosphate bonding and to lubricant reactive effects. It is shown that seizure is delayed if the phosphate coating is annealed at 500°C just before soaping. The γ-Zn3 (PO4 )2 formation which occurs with a decrease in volume induces cracking along hopeite needles and causes an increase in reactive surface for soaping and, therefore, an increase in the quantity of zinc phosphate converted into zinc stearate. Improvement of the phosphate coating by annealing at 500°C before soaping may be an attractive alternative to the use of molybdenum disulfide lubricants.

Copyright © 1992 by The American Society of Mechanical Engineers
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