Preparation And Properties Of The Ni Matrix Coatings In Ultrasonic

With the progress of industry, the improvement of living standards, people put forward a higher demand for the functionality of materials, both the requirements of materials with decorative, ornamental, but also to improve the mechanical properties of materials, such as:hardness, wear and corrosion resisitance. However, these materials with excellent properties are few and expensive. Low carbon steel is the most frequently used in our production and life, whether it is buildings or mechanical parts, are common carbon steel. The disadvantage of low carbon steel is the low strength and hardness, the surface is easy to corrosion, so the low carbon steel are processed by some surface machining technologies, such as: laser in situ growth, sputtering, electroless plating, spraying and electrodeposition. Where laser in situ growth and sputtering technologies are more suitable for use in laboratory studies, rather than industrial production. Spraying is widely used in industrial production, but the quality of the coating is poor compared to the coating synthesized by electrodeposition technology. Relative to the electrodeposition, although the electroless plating method avoids the limitation of the shape of the material, the electrolyte is relatively unstable and the quality of coatings is difficult to control. In general, the electrodeposition technology is relatively simple, low cost,easy to control, with better performance of the coating.In this study, Ni-Mo alloy coating and Ni-Mo/Graphene oxide (GO) composite coating were prepared by DC electrodeposition with ultrasonic-assisted. The effects of different molybdenum molar ratios, current density, ultrasonic power, graphene oxide on the microstructure, grain growth, roughness, hardness and corrosion resistance of Ni-Mo alloy coatings were investigated. The results show that the decrease of Ni/Mo ratio in the electrolyte (the content of molybdenum increasing) can help the nanocrystalline coating change to amorphous structure. When the molar ratio of nickel to molybdenum is 6: 1, the coating is smooth and compact. Nickel molybdenum molar ratio were 10: 1 and 4: 1, some micro-cracks present the coating and the corrosion resistance decreased. Ultrasonic-assisted Ni-Mo alloy coating studies have show that the appropriate ultrasonic power (180 W) can increases the compactness of the coating, accelerates the nucleation rate, reduces the grain size (44 nm) and surface roughness (3.587 nm), increases the hardness (719 HV) and corrosion resistance. Excessive ultrasonic power (270 W) has an adverse effect on the coating,such as increasing the grain size (50 nm), reducing the hardness of the coating (681 HV), and the corrosion resistance.The addition of graphene oxide make the coating covere with a barrier, which can improve the hardness of the coating. The thermogravimetric test shows that the addition of GO improves the high temperature stability of the alloy coatings. EIS and Tafel test results show that the GO elaye the corrosion of corrosive media, the corrosion potential is shifted and the corrosion current density reduces.