The Research on Coating of Electroless Ni-W-P Ternary Alloys

The ternary Ni-W-P alloy coatings were deposited on the surface of Q235 steel using Chemical deposition. The microstructure, phase analysis, plating velocity and hardness were investigated with scanning electron microscope, X-ray diffraction technique and Vickers hardness tester. The results showed that the plating rate had been increased firstly, and then decreased with the increment of sodium citrate concentration in the range of 20-80g/L, the maximum plating velocity was 9.14 mu m/h. The hardness of Ni-W-P plating increased first and then decreased with the increment of sodium citrate concentration, the maximum hardness was 643HV when the concentration of sodium citrate was 40g/L. When the concentration of sodium citrate was 40g/L, the substrate was completely covered by Ni-W-P plating, the surface was composed of uniform crystalline grains, and had no obvious defects and presented amorphous. The coating and substrate were relatively strong, the coating had no the phenomena of fall off and crackle in the bending and files tests when the concentration of sodium citrate was 40g/L and 50g/L respectively.