Tailoring microstructure and properties of nickel-based ternary composite coatings through processing conditions

In this study, Ni-Al2O3-TiO2-WC composite coatings were fabricated using both direct current (DC) and multi-step pulse current (PC) electroplating methods. The metallurgical features, as well as the wear and corrosion behaviours of the deposited layers were evaluated. The results showed that the coatings generated by the pulsed current (PC) method exhibit superior wear and corrosion resistance. Specifically, wear weight loss improved from 12.4 mg (best DC condition) to 8.8 mg in the PC method, while corrosion current density decreased from 7.02E−7 A.cm−2 to 5.95E−7 A.cm−2. The nickel matrix deposits produced via the pulsed method, which included multi-step positive and negative currents with hardness values of 379 and 320 microVickers, were recognised as the most wear-resistant coatings, with a recorded wear weight loss of 7.5 and 6.7 mg, respectively. The incorporation of more than 30 vol.-% of reinforcing particles, together with a compact morphology, significantly enhanced the wear performance. Conversely, the coating produced with a plating current density of 8 A/dm2, with positive, zero, and negative plating current cycles exhibited the lowest corrosion current density (Jcorr = 4.74E−8) despite only containing 10 vol.-% reinforcement. This improvement is attributed to the reduced of micron-cracks and pores and the high compactness of morphology.