Brush Plating of Cobalt/Chromium Carbide Metal Matrix Composite Coatings as an Alternative to Hard Chrome

Wednesday, September 15, 2021: 2:00 PM
227 (America's Center)
Dr. Joshua Thomas , SIFCO Applied Surface Concepts, Independence, OH
Mrs. Danijela Milosevic-Popovich , SIFCO ASC, Independence, OH
The use of hexavalent chromium compounds for the electrodeposition of hard chrome coatings has long been used to improve the hardness, lubricity, wear resistance, and high temperature oxidation resistance of a variety of industrial surfaces and parts. However, concerns for the environment and worker safety from governments around the world have led to a call for alternatives with commensurate properties but safer processing. Metal matrix composites (MMC) such as cobalt co-deposited with chromium carbide have been evaluated as a possible alternative for hard chrome.

MMC coatings consist of both a continuous metal phase and some percentage of small (<100 µm) particles of another chemical species distributed throughout. When these coatings are applied via electrochemical methods, the composition of the plating solution and the plating parameters are vital to the ratio and distribution of these phases throughout the resulting deposit. The ratio and distribution of these phases then determines the properties of the deposit such as hardness.

This presentation will focus on the use of brush electroplating as a method for applying these MMCs. Brush plating is a portable electrodeposition technique where solution is applied to the part by a plating solution saturated sleeve on the anode when contact is made to a localized area. Brush plating can be made portable, typically uses less masking, and less solution is needed compared to traditional tank plating methods. Plating can also be performed at higher current densities than tank plating applications.

Attendees will learn how different particle sizes and concentrations in the plating solution relate to the composition of the resulting deposit. Information will also be shared to demonstrate the importance of plating parameter optimization to the deposit characteristics, such as hardness and wear resistance, of the MMC.