Qi Qiao's research while affiliated with Northeast University At Qinhuangdao Campus and other places

The corrosion resistance of FeCoNiCr high-entropy alloy deposits was investigated upon being prepared by current electrodeposition. The coatings were co-deposited in an electrolyte of an aqueous ferrous, cobalt, nickel, and chromium sulfates solution. Energy dispersive spectrometry analysis demonstrated that all four elements were co-deposited successfully. At the same time, the results from SEM indicate that the surface of the coating exhibits a granular morphology, with uniform density and no presence of cracks, with sizes ranging from 500 nm to 5 μm. Furthermore, X-ray diffraction patterns enunciated that the as-deposited coatings were amorphous. The polarization curves of the FeCoNiCr high-entropy alloy coating were measured by an electrochemical workstation in 3.5 wt.% NaCl, 1 mol·L−1 H2SO4 and 1 mol·L−1 NaOH solutions. The results revealed that the coating exhibited excellent corrosion resistance. The corrosion mechanism of the FeCoNiCr high-entropy alloy coating was analyzed in different environments. Moreover, the scratch testing method was employed to determine the alloy adhesion on the substrate, with higher values obtained for the FeCoNiCr alloy.

Amorphous NiP and NiCrP alloy coatings were prepared on copper substrates by electrodeposition. The thermal stability of the obtained coatings were evaluated by the onset temperature of phase transformation identified with differential scanning calorimetry measurements, and their high temperature oxidation resistances were characterized by the oxidation kinetics curve and the oxidation activation energy. The mechanism of the doping effect of Cr element on crystallization temperature and oxidation resistance of the alloy coatings were discussed based on X-ray diffraction analysis. The results show that the crystallization temperature of NiP amorphous alloy was \(344^{\circ }\hbox {C}\), and the oxidation activation energy was calculated to be \(1.54 \times 10^{\mathrm {3}}\hbox { J mol}^{\mathrm {-1}}\). As for NiCrP alloy coating with a Cr content of 1.8 wt%, the crystallization temperature increased to \(403.8^{\circ }\hbox {C}\) and the calculated oxidation activation energy was \(3.53 \times 10^{\mathrm {4}}\hbox { J mol}^{\mathrm {-1}}\), 2.29 times higher than the NiP coating. The remarkably enhanced high-temperature oxidation resistance of NiCrP alloy coating can be attributed to the compact metal oxide film formed on the surface.

Herein, NiCrP amorphous alloy coatings were prepared on copper substrates by electrodeposition. The aim of this paper is to replace Cr6+ with Cr3+ to prepare NiCrP amorphous alloy coating, which can reduce environmental pollution. By studying the influence of pH, temperature (T), current density (DK), and CrCl3 concentration on the structure, surface morphology, composition, and corrosion resistance of the alloy coatings, the optimum bath formulation and process parameters were determined as follows: 25 g·L−1 NiSO4·6H2O, 100 g·L−1 CrCl3·6H2O, 20 g·L−1 NaH2PO2·H2O, 80 g·L−1 Na3C6H5O7·2H2O (sodium citrate), 40 g·L−1 H3BO3, 50 g·L−1 NH4Cl, 1 g·L−1 KF, 5 g·L−1 C7H5O3NS (saccharin), 0.05 g·L−1 C12H25SO4Na (sodium dodecyl sulfate), and 40 mL·L−1 HCOOH and T: 30 °C, DK: 15 A·dm−2, and pH: 3.5, respectively. NiCrP amorphous alloy coatings with high corrosion resistance were prepared under the abovementioned conditions. The crystal cells of the coating surface are uniform and fine. The corrosion resistance of the NiCrP amorphous alloy coatings was characterized by polarization curves, electrochemical impedance spectroscopy, and an immersion corrosion test and compared with that of the NiP amorphous alloy coating. The results show that Ni91.9P8.1 and Ni83.5Cr8.3P8.2 corrosion potential and corrosion current density are −0.68, −0.44 V, and 36, 7 μA·cm−2 in 3.5 wt.% NaCl, respectively. With Ni91.9P8.1 and Ni83.5Cr8.3P8.2, the maximum weight loss is 61.67 and 15.42 mg·dm−2 in a 1 mol·L−1 HCl, respectively. The corrosion resistance of the NiCrP amorphous alloy coatings in 3.5 wt.% NaCl and 1 mol·L−1 HCl solutions is better than that of the NiP alloy coating.

In the present study, Ni-based alloy coatings were prepared on copper substrates by jet electrodeposition, and their oxidation resistance was evaluated by isothermal oxidation resistance tests at 700, 800, and 900 °C, respectively. The oxidation kinetics of the jet-electrodeposited alloy coatings follow the parabolic rate law. The oxidation resistance of Ni and NiFe coatings is superior to that of jet-electrodeposited NiW coating, while the deposited ternary NiFeW alloy coatings exhibited the highest oxidation resistance. The enhanced high-temperature oxidation resistance could be mainly attributed to the excellent thermal stability of Fe2O3 and NiO phases formed in the alloy coatings during oxidation.

The wetting behavior between a copper substrate with Ni coating and BiCu high-temperature solders were used to investigate the effect of Ni coating between Cu and the BiCu solder. Ni coatings with different thickness were coated on the copper substrate by electrodeposition. The Ni coating acted as a diffusion barrier and reduced the thickness of BiCu/Cu interfacial intermetallic compound (IMC) layer. The failure performance of the BiCu solder alloy was improved significantly without degrading its wettability. And the spread area of the solder decreased with the increasing thickness of Ni coating until 11 μm. Good wettability and failure properties of the BiCu solder alloy were achieved with thicker Ni coating. This would improve the reliability of solder joints and shear strength of welded joints on the BiCu solder alloy.

In this paper, nickel-based alloy coatings were deposited on the surface of pure copper by jet electrodeposition. The wear resistance of the coatings was studied by a material surface comprehensive performance tester under dry sliding. Hardness testing, friction, and wear testing were performed to characterize the microhardness, surface morphology, and wear resistance of the coatings. The results indicated that adding Fe and W could refine and purify the microstructure. The coatings with additions of 5 wt.% Fe and 7 wt.% W exhibited the highest wear-resistant properties. Moreover, new compound phases NiO, Fe 2 O 3 , and WO 3 were found on the surface coatings, such that the microhardness was higher than that in the other coatings. Detailed discussions on the influences of Fe and W on the sliding wear are presented.

In this paper, ternary NiFeW alloy coatings were prepared by jet electrodeposition, and the effects of lord salt concentration, jet speed, current density and temperature on the properties of the coatings, including the composition, microhardness, surface morphology, structure and corrosion resistance, were investigated. Results reveal that the deposition rate reaches a maximum value of 27.30 \(\upmu \hbox {m}\hbox { h}^{-1}\), and the total current efficiency is above 85%. The maximum microhardness is 605 HV, and the wear and corrosion resistance values of the alloy coating are good. Moreover, the ternary NiFeW alloy coating is smooth and bright, and it presents a dense cellular growth. The alloy plating is nanocrystalline and has face-centered cubic structure.

In this paper, ternary NiWP alloy coatings were prepared by electrodeposition, and the effects of sodium hypophosphite (NaH2PO2) concentration on the properties of the coatings, including the deposition rate, current efficiency, composition, surface morphology, corrosion resistance, and microhardness, were investigated. Results reveal that the deposition rate and current efficiency are mainly dependent on the NaH2PO2 concentration in the plating bath. The deposition rate reaches a maximum value of 8.70 μm/h with a NaH2PO2 concentration of 10 g/L, whereas the total current efficiency decreases from 33.10 to 27.80%. As the concentration of NaH2PO2 increases, the grain size of the obtained coatings gradually decreases. Moreover, when the NaH2PO2 concentration is 6 g/L, the NiWP alloy coatings possess a microhardness value of 663.7 HV.

NiWP alloy coatings electrodeposited on pure copper substrates with additive saccharin (C7H5NO3S) contents of 0-6 g/L were investigated via scanning electron microscope (SEM), x-ray diffractometer, microhardness, polarization curves, deposition rate, and wear resistance. Results show that the corrosion resistance, microhardness, and wear resistance of the NiWP alloy coatings have been optimized with the increase in saccharin contents changing from 2 to 4 g/L. The morphology of the NiWP alloy coatings observed via SEM exhibits a typical spherical nodular structure. The increase in saccharin content will decrease crack formation. The phases of NiWP alloy coatings are mainly the mixture of amorphous and microcrystalline nickel. Moreover, the quality of the coating can be improved through a slight change in the deposition rate. The hardness of the NiWP alloy coating continues to increase from 530.5 to 630.5 HV with the increase in saccharin content from 0 to 6 g/L. In addition, the P and W contents in the alloy coating are increased from 8.29 to 8.66 wt.% and from 28.68 to 30.45 wt.%, respectively. The corrosion potential is varied from −0.332 to −0.247 V, and the current density is varied from 23.81 to 3.282 µA/cm2 when the saccharin content is in the range of 0-4 g/L. With the increase in saccharin content from 0 to 4 g/L, the wear loss decreases gradually. Subsequently, a plateau is reached when the saccharin content is higher than 4 g/L. NiWP coatings show better tribological performances under high rotational speed than those under low rotational speed. Several possible reasons have been discussed.

The effect of plating temperatures between 60 and 90°C on structure and corrosion resistance for electroless NiWP coatings on AZ91D magnesium alloy substrate was investigated. Results show that temperature has a significant influence on the surface morphology and corrosion resistance of the NiWP alloy coating. An increase in temperature will lead to an increase in coating thickness and form a more uniform and dense NiWP coatings. Moreover, cracks were observed by SEM in coating surface and interface at the plating temperature of 90°C. Coating corrosion resistance is highly dependent on temperature according to polarization curves. The optimum temperature is found to be 80 ∘ C and the possible reasons of corrosion resistance for NiWP coating have been discussed.