Investigation of the Enhancement Mechanism of Electrochemically Deposited Ni–Co–W Coatings via Laser Irradiation: Effect of W Contents on Corrosion Resistance

Abstract

Ni−Co−W is an alloy with excellent overall performance and wide application prospects. Electrochemical deposition of Ni−Co−W alloys is currently the most promising process for replacing hexavalent chromium plating. Variations in the W content of the Ni−Co−W coating significantly affect its surface morphology, internal structure, and mechanical properties. Considering the numerous defects with conventional electrochemical deposition, a laser was introduced to enhance the quality and rate of deposition. Using a multienergy composite field, the deposition technique enhanced various properties at room temperature. Ni−Co−W alloy coatings were fabricated through electrochemical deposition and laser electrochemical deposition using electrolytes containing Na 2 WO 4 •2H 2 O at concentrations of 12, 15, 18, and 24 g/L in this investigation. This study aimed to examine how laser irradiation strengthens the corrosion resistance of the coatings. The corrosion resistance could be enhanced with an initial W content increase, but the corrosion resistance did not depend entirely on the W content. Variations in the W content of the electrochemically deposited coatings affected the surface morphology, residual internal stresses, and crystal structure, changing the corrosion resistance. In contrast, the laser electrochemical deposition coating was caused by the combined effect of the W content and laser irradiation (concentration of <18 g/L). Laser electrochemical deposition of the Ni−Co−W coating resulted in a higher W content than electrochemical deposition (≥3.5%), improved the residual internal stresses, and refined the grain size of the coating, resulting in better corrosion resistance (corrosion rate decreased by 74% and R ct increased by 109.1% at most).