Microstructure and properties of Ni-nano TiC composite coating prepared by different electrodeposition methods

To improve the quality of electrodeposited Ni-nano TiC composite coating, the Ni-nano TiC composite coating was prepared on the Q235 steel by electrodeposition. The effects of three different electrodeposition methods of direct current (DC), single pulse and double pulse on the microstructure and surface properties of the composite coating were compared and analyzed. The surface morphology and element distribution of the coatings were analyzed by SEM / EDS. The phase and grain size of the coatings were studied by XRD, and the hardness and corrosion behavior were tested by microhardness tester and electrochemical workstation respectively. The results show that the compactness and microhardness of the composite coating increase in turn, and the porosity, the plating rate and grain size decrease in turn according to DC, single pulse and double pulse electrodeposition methods. The content of TiC in pulse deposition composite coating is obviously less than that in DC deposition coating. The microhardness of double pulse electrodeposition composite coating is 740.5 HV, which is 67% higher than that of DC electrodeposition coating. Compared with DC and single pulse electrodeposited coatings, the self-corrosion current density of double pulse electrodeposited composite coatings in 3.5wt% NaCl solution decreases by an order of magnitude ( 5.275 × 10−6 A·cm−2 ), the self-corrosion potential shifts positively ( −0.113 V ), and the charge transfer resistance is the largest, showing the best corrosion resistance.