Fabrication of macrocrack-free thick chromium duplex plating for remanufacturing applications

Abstract

The remanufacturing process of a hydraulic cylinder rod becomes a challenging prospect in the industrial sector producing heavy equipment. That is because remanufactured components can have the same product quality as new components with a more economical price. Hard chromium electrodeposition is a well-known technique to provide a protective coating for the cylinder rod so that it has favorable wear and corrosion resistance properties. Associated with remanufacturing applications, the used chromium plating covering the cylinder rod should be removed first before applying the new chromium one. Whereas the removal process often slightly consumes the base metal and fresh thicker chromium should be deposited in order to preserve its original diameter. The main problem is that the thick chromium may experience macrocrack after the baking process at 200 °C. Hence, the observation of as-plated and as-baked thick and hard chromium deposit properties is the novelty of this research. In this work, the thick and hard chromium plating over a flat carbon steel substrate was produced by the electrodeposition method. A conventional single-layer chromium deposit with a plating current density greater than 40 A/dm2 shows macrocracks after the baking process at 200 °C for an hour. For the chromium duplex plating composed of two Cr layers, the maximum thickness of the deposit was 261.0±8.5 microns, and the macrocrack was observed. Meanwhile, the as-baked duplex chromium plating composed of a polished Cr-C layer and a Cr layer has a microcrack density of 337±8 cracks/cm and hardness of 924.8±22.2 HV0.3 without macrocracks. EPMA characterization confirmed the presence of a carbon element in the Cr-C layer, and it is presumed due to carbon co-deposition from formic acid additives.