Study On The Improvement Of Performance Of Ni-W-P Coatings After Heat Treatment

Amorphous Ni-based alloy electroless coating had been widely used in industry due to its good performance of corrosion resistance. Better corrosion resistance was obtained by adding tungsten to binary Ni-P alloy to form ternary Ni-W-P alloy coating.An optimal formula of Ni-W-P alloy was developed trough orthogonal array testing strategy. The corrosion resistance of Ni-P, Ni-W-P coatings, heat treated at 400℃,500℃,600℃,700℃, were compared. The results indicated that the corrosion resistance of Ni-W-P coatings were sharply improved which were 1.5～8 times than Ni-P coatings and was up to 3.1 times than as-plated amorphous Ni-W-P coating. The reason were thought to be:the improvement of compactness due to the diffusion of elements in the coatings during the heat treatment and the formation of protective NiO+WO3 mixed oxide film.Dropwise condensation were attained on both as-plated and heat-treated Ni-W-P coatings. The performance of heat transfer were sharply approved. The heat transfer coefficient of as-plated and heat-treated Ni-W-P coating were 1.2～2.5 and 1.5～3 times than filmwise condensation respectively.