1988 年 39 巻 12 号 p. 809-812
A study was conducted to determine the maximum obtainable tungsten content in the alloy, using ammoniacal alkaline citrate baths of pH7.5-9.0 at 80°C. Sodium citrate and citric acid were considered as the complexing agent. The presence of a large amount of sodium in the bath reduced tungsten content and current efficiency. When a suitable amount of sodium tungstate and nickel sulfate were added to the citric acid baths, alloys up to 51wt%W, corresponding to Ni3W, were obtained. Since alloys exceeding 40wt% W were obtained for the first time, X-ray examination and hardness testing were also conducted. Alloys exceeding 44wt% W (Ni4W stoichiometry) were amorphous, having extremely small atomic size. The Vickers hardness of the 44wt% W alloy was Hv 1350 after heating at 550°C for 1h.