Electrodeposition of Co-W Nanocrystalline Alloy Coatings under Ultrasonic Irradiation Action

Ultrasonic irradiation was utilized to improve the microhardness and corrosion resistance of Co-W nanocrystalline coatings on cabon steel substrate.The composition and microstructure of the coatings were characterized by XRD,EDX and SEM.The results showed that the coatings exhibited hexagonal close-packed (hcp) crystal structure,which became compact and smooth with the decrease of grain size and internal stress due to the application of a proper ultrasonic power(40-100 W).The tungsten content in coatings increased with the increase in the applied ultrasonic power.It is interesting to find that the coatings with tungsten content higher than 20% was not exhibit amorphous.Smaller grain size,higher tungsten content and lower density of surface defects favor the improvement of the hardness and of the corrosion resistance for Co-W nanocrystalline coatings.