Abstract
A new method has been developed to lubricate metal coin blanks during the coin production process. The lubricant is formed on the metal surfaces as a monomolecular film during burnishing, which provides an exceptional combination of chemical and tribological environments needed to promote reaction. Laboratory-scale burnishing simulations combined with surface analysis indicated the composition and nature of the films formed. A comparison of reactions on metal surfaces with and without burnishing confirmed the importance of the tribochemical process to the successful lubrication of the blanks. Implementation of this lubrication procedure to production lines has improved the surface quality of the coins and tripled the die life, resulting in considerable cost savings.
Acknowledgments
This article not subject to US copyright law
Review led by Liming Chang
Notes
*Certain commercial equipment, instruments, or materials are identified in this article to adequately specify the experimental procedure. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose.