The Studies Of Electrodeposition And Performance Of Amorphous Fe-Co-W, Ni-Co-W Alloy Deposits For Chromium Replacement

For decades, chromic acid and sulfuric acid were employed in chromium electroplating. The bath composition was simple and the process was easy to operate. Satisfactory results were obtained in the production of both decorative and functional chromium. However, there were many defects in conventional chromium plating, such as low current efficiency, poor throwing and covering power of plating bath, and acidic, oxidated, corrosive, and toxic plating bath. The hexavalent chromium in solution was recognized as a carcinogen. The use of hexavalent chromium was restricted. Therefore, the plating researchers in the world have been seeking for technologies for chromium replacement.In recent years, electrodeposited amorphous tungsten-based alloy deposits were regarded as one of potential chromium substitutes for many of their excellent properties, such as decorative appearance, high thermal stability, high hardness, good wear and corrosion resistance, high catalytic activity, good magnetic properties, and its potential engineering applications. Compared with chromium plating, there were many advantages in electrodepositon of amorphous tungsten-based alloy deposits, for example, high current efficiency, good throwing and covering power, environmently friendly. So, rencently there were extensive interists in the electrodeposition of amorphous tungsten-based alloy deposits. Few reports about the electrodeposition and their propertoies of amorphous Fe-Co-W, Ni-Co-W alloy deposits were presented. In this thesis, following reserches were studied in detail.1. The effects of bath composition and process on the appearance, composition, and microhardness of amorphous Fe-Co-W alloy deposits were studied comprehensively for the first time. The optimum plating bath and palting variables for eletrodeposition of amorphous Fe-Co-W alloy deposits were chosen.2. The effects of heat treatment temperature on the microstructure, microharness, and wear resistance of amorphous Fe-Co-W alloy deposits were investigated primarily. A comparative study was made with the microhardness, and wear resistance of chromium deposit. The optimum heat treatment temperature to obtain good properties was provided.3. The effects of deposits composition on the corrosion resistance property of amorphous Fe-Co-W alloy deposits were examined for the first time. A comparativestudy was made with the corrosion resistance of chromium deposit.4. The effects of plating variables on the appearance, deposit composition, and microhardness of amorphous Ni-Co-W alloy deposits were studied, and the optimum palting variables were obtained.