In recent years, alloy and alloy-ceramic coatings have gained a considerable attention owing to their favorable physicochemical and technological properties. In this review, we investigate Ni, NiCo alloy and NiCo–ceramic composite coatings prepared by electrodeposition. Electrodeposition is a versatile tool and cost-effective electrochemical method used to produce high quality metal coatings. Surface finish and tribological properties of the coatings can be further improved by the addition of suitable agents and control of deposition operating conditions. In this review, Ni, NiCo alloy and NiCo–ceramic composite coatings prepared by electrodeposition are reviewed by critically evaluating previous researches. The use of the coatings and their potential for future research and development are discussed.

In order to improve the wear and seawater corrosion resistance of metals, Ni–Co–P alloy coatings were fabricated on 45 steel substrates with jet electrodeposition in different jet voltages and temperatures of plating solution. The cross-section morphology, chemical composition, crystalline structure, microhardness, wear, and seawater corrosion resistance of the samples were analyzed and characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), microhardness tester, friction wear tester, and electrochemical workstation, respectively. The results showed that the contents of Co in Ni–Co–P alloy coatings changed with the variation of jet voltages and temperature of plating solution. The content of Co in Ni–Co–P alloy coatings reached a maximum value of 47.46 wt·% when the jet voltage was 12 V and the temperature of the plating solution was 60 °C. The XRD patterns of Ni–Co–P alloy coatings showed that there was an obvious preferred orientation in the (111) plane. With an increase in the jet voltages and temperature of the plating solution, the microhardness of Ni–Co–P alloy coatings first increased and then decreased, with the maximum value obtained being 634.9 HV_0.1. When the jet voltage was 12 V and the temperature of the plating solution was 60 °C, the wear scar width of the Ni–Co–P alloy coatings reached a minimum value of 463.4 µm. In addition, the polarization curves in the electrochemical test indicated that the samples deposited at 60 °C and 12 V exhibited the lowest corrosion current density (I_corr) of 1.72 µA/cm² and highest polarization resistance (R_p) of 19.61 kΩ·cm⁻², which indicated that the coatings had better seawater corrosion resistance.

Type 45 steel substrate surfaces were coated with Ni–Co–P alloy coatings using jet electrodeposition in varying reciprocating sweep speed and jet gap to improve the wear and seawater polarization resistance of the substrate surface. The properties of the deposited coatings were analyzed and characterized. The results showed that the morphologies of the cross-section, thickness, and chemical composition of coatings were affected by reciprocating sweep speed and jet gap variation. At a reciprocating sweep speed of 175 mm·s⁻¹ coupled with a jet gap of 2.0 mm, the content of Co element in the deposit attained the highest value of 47.66 wt.%. Reciprocating sweep speed and jet gap variation exhibited no significant influence on either the phase structure or the peak intensities of deposited Ni–Co–P coatings, but an obvious preferred orientation was evident in the (111) plane. Further increase in reciprocating sweep speed and jet gap caused an initial increase in the microhardness of Ni–Co–P alloy coatings followed by a decrease, where the highest value attained was 635 HV_0.1. At a jet gap of 2.0 mm and a reciprocating sweep speed of 175 mm·s⁻¹, Ni–Co–P alloy coatings reached a minimum wear scar width value of 460 µm. Electrochemical tests showed that the seawater corrosion resistance of coatings exhibited an observable change with increased reciprocating sweep speed and jet gap. The Ni–Co–P alloy coatings exhibited the highest polarization resistance (R_p) of 28.32 kΩ·cm⁻² when the reciprocating sweep speed was 175 mm·s⁻¹ and the jet gap was 2.0 mm, which indicated that the coatings had better seawater corrosion resistance.

In this study, a grit-blasting pretreatment was used to improve the adhesion, corrosion resistance and microhardness of Ni-W/SiC nanocomposite coatings fabricated using the conventional electrodeposition technique. Prior to deposition, grit blasting and polishing (more commonly used) pretreatments were used to prepare the surface of the substrate and the 3D morphology of the pretreated substrates was characterized using laser scanning confocal microscopy. The coating surface and the cross-section morphology were analyzed using scanning electron microscopy (SEM). The chemical composition, crystalline structure, microhardness, adhesion and corrosion behavior of the deposited coatings were characterized using energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), a microhardness tester, a scratch tester and an electrochemical workstation, respectively. The results indicated that the grit blasting and SiC addition improved the microhardness, adhesion and corrosion resistance. The Ni-W/SiC nanocomposites pretreated by grit blasting exhibited the best adhesion strength, up to 36.5 ± 0.75 N. Its hardness was the highest and increased up to 673 ± 5.47 Hv and its corrosion resistance was the highest compared to the one pretreated by polishing.

In this study, Ni–Co–P–BN(h)–Al₂O₃ binary nanocomposite coatings were fabricated on steel C1045 substrates by jet electrodeposition. The samples were then processed using self-made laser processing equipment to investigate the influence of long-pulse laser processing parameters variation on samples’ surface morphology, roughness and wettability. Additionally, the properties of samples before and after laser processing were analyzed and characterized. The results showed that the surface morphologies, surface roughness and wettability of samples were affected by laser output power, pulse width and spot-to-spot distance variation. A convex dome was formed on the samples’ surface at a low laser output power and a suitable pulse width, while a dimple was formed on the samples’ surface at a high laser output power. The surface roughness and water contact angle of samples increased with the rise in laser output power or pulse width. The water contact angle decreased with the rise in the spot-to-spot distance, and the water contact angle reached a maximum value of 139.8° with a laser output power of 50 W, a pulse width of 100 µs and a spot-to-spot distance of 150 µm. The samples after laser processing exhibited a higher wettability, microhardness and wear resistance compared to those of the normal samples. The microhardness of the heat-affected zone reached a maximum value of 812.1 HV_0.1, and the wear scar width of the samples reached a minimum value of 360.5 µm. However, after laser processing, the samples’ seawater corrosion resistance decreased slightly.