Cobalt/Chromium Carbide Composite Coatings Applied By Brush Plating for Use As an Alternative to Hard Chrome

Abstract

Due to increased concern for both environmental and worker safety from governments around the world, numerous significant industrial chemicals are being phased out of production processes. One example is the use of hexavalent chromium compounds for the electrodeposition of hard chrome. Electrodeposited chrome is typically used for improved hardness, lubricity, wear resistance, and corrosion resistance. This work will support the use of a metal matrix composite composed of cobalt and chromium carbide particles as an alternative for chrome coatings deposited from hexavalent chromium compounds.Metal matrix composite (MMC) coatings consist of two phases co-deposited during plating: a continuous metal phase such as cobalt and small (<100 µm) particles of another chemical species distributed throughout. The physical qualities of the composite (such as hardness) are strongly dependent on the ratio and distribution of the two constituent phases. The composition of the plating solution and the parameters used during plating both play important roles in the composition and quality of the final deposit.While most research has focused on applying metal matrix composites by tank electroplating methods, this presentation will focus on applying the coating via brush plating. 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 operations typically use less masking when plating small areas of a larger part. Less solution is needed because the part does not need to be immersed. And the brushing action allows for faster solution replenishment at the electrode surface.During this presentation, attendees will be shown examples of a matrix material of cobalt co-deposited with either 1 µm or 6 µm chromium carbide particles. Attendees will learn how the concentration of the particle in solution determines the range of particle incorporation; as well as understand how tailoring the plating parameters to the system of particle and matrix is vital to creating a deposit for their specific characteristics.