Effect Of P Contents On Nanocrystallisation And Corrosion Behaviour Of Electroless Ni-W-P Plating

Prepared by chemical deposition Ni-W-P plating two components, the ingredients were M (Ni-4.83% W-11.26% P) and N (Ni-4.90% W-5.98% P), The use of X-ray diffraction (XRD), and combined with Jade software, quantitative analysis of the phase composition of the coating, the degree of crystallization, the grain size and lattice micro-strain; By electrochemical polarization experiments,Vickers hardness measurements and scanning electron microscopy (SEM) and optical microscopy to observe the two coating surface morphology before and after heat treatment and corrosion around, studied the phosphorus content of the chemical deposition Ni- WP alloy Heat Treatment and corrosion Behavior of crystallization. The main conclusions are as follows:Through the above detection means, the coating M with high P contenthas a higher degree of amorphization, a denser plated surface morphology, while N with a relatively low P content of the coating present some tiny pores on the surface.After the heat of crystallization, the tiny gap will gradually disappear as a result of atomic diffusion.In its crystallization process, cellular blurred edges becomesmooth.X-ray diffraction analysis showed that the as-plated state of coating M with high P content was amorphous structure, while the lower P content of coating N is mixed with crystalline structure and an amorphous phase consisting of Ni crystallites.When the temperature rises, the Ni phase precipitateand more and more amount of precipitation occurs. When the temperature continues to rise and Ni3P precipitated phase began to precipitate and grow.The hardness of two coatings has the same trends with the temperature rises, when the temperature continues to raise, the hardness increase first and then decrease.N reaches the maximum hardness value at the heat treatment temperature of 400℃ of crystallization, while M reaches the maximum hardness value at the heat treatment temperature of 500℃ of crystallization. When the temperature is high, hardness began to decline, but the high P content of the coating declines relatively slow, mainly because grain size and the number of Ni and Ni3P phases. The coating has the largest micro-strain at as-plated state, and with annealing temperature increases, the micro-strain value decreased. When the annealing temperature at 300～400℃, the micro-strain value appears plunged. Micro-strain value of M is much larger than N at low temperatures, indicating that P has an effecton increasing the micro-strain values.From Etched surface morphology and anodic polarization curves under different heat treatment conditions we can find that the two coatings corrode uniformly in 0.5mol/L H2SO4 solution. P improves the corrosion resistance at a low temperature.