Influence of Surface Modification of Powdered Metals on Fabrication of Electrical Laminate Contacts

Previous testing was completed on copper silver graphite electrical laminates. Prior to adding a silver coated copper interlayer; silver diffused into copper faster than graphite, which caused graphite accumulation at the interface creating weak bonding to occur. Upon the addition of a silver coated copper interlayer, counter diffusion occurs between the silver graphite and the silver coated copper interlayer which eliminates graphite accumulation at the interface. Using the scanning electron microscope, it was shown that very small amounts of graphite diffused into the interface. Building upon our previous results, the study extended the use of this laminate method to other PM materials that are used for electrical contacts namely copper silver tungsten laminates. Laminates using the modified copper powders were fabricated and the impact of surface modification on mechanical, electrical and wear resistant properties were assessed. Interlaminar shear strength was measured using a shear testing fixture; while electrical performance was measured using a micro ohm electrical tester. Wear resistance testing still has yet to be completed and will be accomplished with the help of local PM industry. Further study of microstructure and modification of powder interface was done using the characterization facilities available at Penn State DuBois and Materials Characterization Laboratory at University park.