Investigation Of Amorphous Ni-W-P Alloy Prepared By Jet Electrodeposition

Amorphous Ni-P-W alloy is widely used for in mechanical, electronic and chemicalindustry, etc. thanks to its unique structure and excellent properties of outstanding catalyticactivity of hydrogen evolution, good corrosion resistance, good wear resistance andmechanical properties. However, the preparation of Ni-W-P alloys by conventionalmethods exists too many restrictions to get effective applications. Aiming at this problem,the main purpose of this work is the successful preparation of compactive amorphousNi-W-P alloy by a new method of electrolyte jet electrodeposition （JED）.This paper mainly studied the main composition and concentration of electrolyte ofpreparation of Ni-W-P alloy by jet electrodeposition, and the effects of depositing processparameters, such as jet speed, current density and pH on the deposition rate, currentefficiency, surface morphology, chemical composition and the structure of the coatings ofNi-W-P alloys were investigated.The experimental results indicate that the current density of the jet electrodepositionas a high-speed electroplating technique with special flow characteristics, compared withthe conventional electroplating, are both enlarged largely owing to the promotion ofplating solution. This is the mechanism of the refining grain size and increasing depositingrate. In the composition of plating solution, increase the concentration of nickelous sulfatecan enhance he deposition rate, but cut down the content of tungsten in the coating.Tungsten, phosphorus can be induced by nickel ions, which increase the concentration ofsodium tungstate is helpful to obtain high content of tungsten coating. The content ofsodium hyphosphite in the plating solution has a strong role in promoting the formation ofamorphous alloys. Sodium citrate as complexing agent increases the difficulty of the metalion precipitation by adding too much. The deposition rate is accelerated, the coating iscompacted and cut down the content of tungsten when increasing jet speed. Increasing thecurrent density can lead deposition rate increases, current efficiency drops, and highcurrent density will affect the coating quality. The increasing of pH is helpful to tungstendeposit, but affect the deposition rate. On the bases of the individual factor,the following result is required: NiS_O4·6H₂O26g/L、Na₂WO₄·2H₂O75g/L、H₃BO₃35g/L、NaH₂PO₂·H₂O15g/L、C₆H₅Na₃O₇·2H₂O70g/L,the current density （J）:20A·dm^-2, Temperature:50℃, pHvalue:6.5. And thecharacterization of the samples prepared under that condition is carried out by scanningelectron microscopy （SEM）, X-ray diffraction （XRD）, diffusion scanning calorimetry（DSC） and nano indentation.The results are shown that Ni-W-P alloy coatings arecomposed of Ni79.24%、W4.28%、P13.96%and present an amorphous structure whichthe crystallization temperature of the coating is376.5℃. After heat treatment, it is foundthat the coating structure changes from amorphous to crystalline. and the coating hardnessis increased nearly three times.