| Composite coatings consisting of a Ni-Co alloy matrix reinforced with ZrO2 particles?average size of 50 nm? were synthesized by electrochemical deposition assisted by an external ultrasonic field.The effects of cathode current density,concentration of ZrO2 particles,ultrasonic power,bath temperature and plating time on hardness,wear loss and thermal stability of Ni-Co/ZrO2 composite coatings were investigated with single variable method.The kinetics of electrodeposition was investigated using linear sweep voltammetry,cyclic voltammetry and electrochemical impedance spectroscopy.Scanning electron micrographs,X-ray diffraction and energy dispersive spectrum were employed to characterize the morphology and composition of the coatings.And the microhardness,nanohardness,elastic modulus,die ratio,corrosion resistance and tribological properties was investigated through the micro hardness tester,nano indentation,electrochemical workstation and rotating friction test instrument.The experimental results show that:?1?the optimized technological conditions are:cathode current density,5 A/dm2;concentration of ZrO2 particles,10g/L;bath temperature,60?;plating time,60min;?2?The electro-crystallization of Co2+ was governed by a three-dimensional“nucleation/growth”process.The co-deposition of alloy and composite starts at-0.72 V and-0.70 V,respectively.The results also shows that polarizability of the composite system is smaller with the addition of ZrO2 particles and the ZrO2 improved the electrode process.?3?It was found that,when the addition of ZrO2 is 10 g/L,coating nanohardness,elastic modulus and the ratio of nanohardness to elastic modulus increased to 6.13 GPa,291 GPa and0.026;corrosion voltage and corrosion current are-0.22V and17.09×10-6A/cm2;friction coefficient and wear loss decreased to 0.3273 and0.85 × 10-5g·m-1;?4?Results revealed that tribological propeties of coating could be improved significantly by incorporating ZrO2 simultaneously with ultrasonic. |
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