Influence of Current Mode on Microstructure and Mechanical Properties of Nano-TiN/Ni Composite Coatings

Nano TiN/Ni composite coatings were prepared on 45 steel substrate by the ultrasonic-electrodeposition method with a nickel sulfamate electroplating solution containing nano-TiN particles. The effects of the three current modes of direct current, single pulse and positive-negative pulse on surface morphology, nano-TiN content and distribution, interface binding force, microhardness and friction-wear performance of the coatings were compared and studied. The results show that compared to those by direct current electrodeposition, the grains of the pusle electrodeposited coating were finer, the surface was smoother, the surface cracks was fewer and the interface binding force was higher. The interface binding force of the positive-negative pulse electrodeposited coating was higher than that of single pulse electrodeposited coating. It was relatively easy for the pulse electrodeposition to deposite nano-TiN particles. The nano-TiN particle deposition rate by positive-negative pulse electrodeposition was higher than that by single pulse electrodeposition. The microhardness of the positive-negative pulse electrodeposited coating was the highest and its friction-wear performance was the best, while those of the direct current electrodeposition coating were the worst.