The hardness and wear resistance of amorphous Al–Mn alloy coatings can be improved by incorporating ceramic particles into them to extend their application. In this paper, Al–Mn/WC composite coatings have been prepared with electrodeposition in stirred AlCl3–NaCl–KCl–MnCl2molten salts at 180 °C with the addition of WC particles. The effects of stirring speed (400–700 rpm) and cathode current density (15–75 mA/cm2) on the produced Al–Mn/WC composite coatings have been studied. At 600 rpm and 700 rpm, the Al–Mn/WC composite coatings exhibited the best uniform distribution of the embedded WC particles, with the tested microhardness value up to 650 HV0.1, compared with 530 HV0.1of the Al–Mn alloy. Moreover, under various cathode current densities, the best quality of the Al–Mn/WC composite coating was obtained at 55 mA/cm2, with a homogeneous distribution of WC particles and the highest microhardness value (670 HV0.1). It is expected that this method could be extended to be applied for the preparation of aluminum-based and magnesium-based ceramic composite coatings.Keywords:AlCl3–NaCl–KCl–MnCl2molten salts;electrodeposition;WC particles;Al–Mn/WC composite coating
Hui Jin,Renjie Ji,Tiancong Dong,Shuo Liu,Fan Zhang,Lilong Zhao,Chi Ma,Baoping Cai,Yonghong Liu
Nickel-iron alloy is broadly utilized in the industrial field due to its fabulous mechanical properties. How to prepare nickel-iron alloy with better corrosion resistance more efficiently is an important concern. Based on this, the WC particles enhanced nickel-iron coatings were fabricated by jet electrodeposition (JED) at a high current density of 100A/dm 2 . It was found that increasing the deposition temperature appropriately during JED is beneficial to obtain Ni-Fe-WC coating with the higher number of hard particles. Specifically, the maximum WC particles proportion reaches 4.47 wt% at 55 °C. The electrochemical corrosion behavior of coating was measured by polarization curve and electrochemical impedance spectroscopy (EIS). The polarization curve test results displayed that the E corr positively shifted from −0.402 to −0.281 V and the i corr reduced from 25.13 to 7.05 μA/cm 2 with the increase of WC particles proportion. Meanwhile, the EIS test results exhibited that the impedance of coating enhanced from 12,720 to 59,140 Ω cm 2 . The neutral salt spray test (NSS) was used to simulate the corrosion of coating in a seawater environment. The NSS results showed that with the increase of WC particles, the corrosion products decreased gradually and the degree of corrosion decreased. The analysis showed that WC particles can help the grain growth and release the internal stress in the coating. Larger grain sizes reduces intergranular corrosion and smaller internal stress help to alleviate stress corrosion cracking. The above research can provide theoretical support for the efficient preparation of particle enhanced composite coating with strong corrosion resistance.
One type of multimodal (comprised of nanometer and sub-micrometer WC particles) and two types of conventional (comprised of nanometer and sub-micrometer WC particles, respectively) WC/Co powders were deposited on AISI 304L stainless steel substrates by using high velocity oxygen fuel spraying. The use of multimodal WC particles was indicated to have a beneficial effect on the solar absorptance (α) of the WC/Co coatings. The α of the multimodal WC coating reached 0.87, which was much higher than what can be achieved by either fine (0.82) or coarse powders (0.80) alone. By microstructural analysis, the enhancement in solar absorptance of the multimodal WC/Co coating was ascribed to the layer of distributed WC particles. During the thermal spraying, the nanostructured WC particles underwent rapid melting for the large specific surface area while the aggregated powders were heated, but not necessarily melted. The molten nano-WC would fill the available pores between the softened and heated aggregates, providing a layered distribution of WC particles for the spray-deposited coating. In this condition, the light-trapping in the multimodal coating will be enhanced due to the efficient light reflection among the multimodal WC particles, which contributes to the enhancement of solar absorptance.Keywords:solar selective absorbing coating;high velocity oxygen fuel;selective absorbing properties
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