| Ni-Fe alloy coating has been applied widely to chemical, textile, aviation, automotive and computer fields due to its excellent corrosion resistance, wear resistance and good weldability. However, Ni-Fe coating has a great limit for the use of the mechanical equipment because of its larger friction coefficient. The PTFE is composed of the monomer polymer tetrafluoroethylene. It has stable performance, such as excellent chemical stability, good heat and cold resistance and very small friction coefficient. In order to further improve the performance of Ni-Fe coating, decrease the friction coefficient while keeping the original good performance.The PTFE particles, nickel and iron were deposited by dispersing the polymer PTFE in the Ni-Fe alloy plating solution. The composite coatings will have good comprehensive properties.The preparation of two kinds of composite coatings including Ni-Fe-PTFE and Ni-Fe were finished by electroplating under different experimental parameters. The microstructure, element content, interface binding state, hardness and corrosion resistance, phase composition of the coatings were studied by using the field emission scanning electron microscope, energy spectrometer, micro hardness tester, electrochemical workstation, XRD and other equipments. The influence of temperature, cathode current density, stirring mode,PH value, and PTFE particle on the properties of the coating was studied by single factor experiment in this paper.The result showed that the Ni-Fe-PTFE composite coating is more uniform, brighter,flatter and compacter compared with the surface of the Ni-Fe coating.The friction coefficient of composite coating is greatly reduced and be only about sixty-five percent of Ni-Fe alloy coating. The hardness of the composite coating is decreased and wear be increased due to the addition of soft PTFE particles. The corrosion resistance of the composite coating were investigated using the electrochemical experiments and the results showed that the impedance of the two coatings is 482??cm and 17202??cm respectively. The impedance of the Ni-Fe-PTFE composite coating is closely 30 times than Ni-Fe coating. It means that the Ni-Fe-PTFE composite coating has good corrosion resistance in 3.5% NaCl solution.The properties of the composite coating under different parameters showed that the additions of PTFE is the main factor that affecting the properties of Ni-Fe-PTFE composite coating. The stirring method and speed affects directly the dispersion of PTFE in the plating solution. The cathode current density, temperature, PH value and stirring speed have little effect within a certain range.Considering comprehensively the surface morphology, the mechanical properties and corrosion resistance of Ni-Fe-PTFE composite coatings indicated that the best plating process is the following : the amount of PTFE is 9g/L, the cathode current density is4.0A/dm2, the bath temperature is 50℃, PH value is 4, the stirring method is mechanical plus ultrasonic stirring, the mechanical stirring speed is 150 r / min, Ultrasonic agitation frequency is 60 Hz / min. |
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