The corrosion of steel structures in aggressive marine environments is a vital issue that induces significant degradation of their performance and lifespan. Herein, three arc-sprayed ZnAl coatings with varied Al contents of 0 wt.%, 15 wt.%, and 50 wt.% were deposited onto a hull steel substrate. The effect of Al content on the long-term corrosion protection performance of ZnAl coatings left in a chloride-containing solution for 840 h was systematically investigated. The evolutions of open-circuit potential, polarization curves, and electrochemical impedance spectroscopy of different ZnAl coatings during the long-term immersion test were examined. The morphologies and phase constitutions of the corrosion products were characterized. The results indicated that the corrosion rate of ZnAl coatings decreased as the Al content increased, and the ZnAl50 coating exhibited the most superior long-term corrosion protection performance. Moreover, for the three ZnAl coatings with an Al contents varying from 0 to 50%, their corrosion rate increased with immersion time in the initial 360 h due to the formation of the unstable and porous corrosion product ZnO; after 360 h immersion, their corrosion rate decreased with the prolonging of immersion time. This was revealed to be related to the formation of different corrosion products. ZnO and stable Al₂O₃ were the main corrosion products for the pure Zn coating and ZnAl15 coating, respectively. Al₂O₃ and powerful layered double hydroxide Zn₆Al₂(OH)₁₆CO₃·4H₂O were found to be the dominant corrosion products of the ZnAl50 coating, which was responsible for its remarkable long-term corrosion protection performance.

In this work, to explore potential substitutions for the Co binder phase, ultrafine-grain WC-based cermets with various binder phases of Co, Ni and AlCoCrNiFeCu HEA were prepared using the SPS method. Based on SPS, WC-based cermets were fabricated at higher speed, showing fine carbide particles less than 410 μm. The microstructure, mechanical properties and wear properties were systematically evaluated. By comparison, the grain size of WC was the lowest for WC-10Co, while WC-10 HEA cermet held the coarsest WC particles. The hardness and fracture toughness of WC-10 HEA were the best among all three samples, with values of 93.2 HRA and 11.3 MP·m^1/2. However, the bending strength of WC-10HEA was about 56.1% lower than that of WC-10Co, with a value of 1349.6 MPa. The reduction in bending strength is attributed to the lower density, formation of a newly Cr-Al rich phase and coarser WC grains. In dry sliding wear conditions, WC-10 HEA showed the lowest wear rate (0.98 × 10⁻⁶ mm³/(N·m)) and coefficient of friction (0.19), indicating the best wear resistance performance. This reveals that WC-based cermet with a HEA binder phase has superior wear performance due to the higher hardness and good self-lubricating effect of the wear products.

Burning loss of graphene in the high-temperature plasma-spraying process is a critical issue, significantly limiting the remarkable performance improvement in graphene reinforced ceramic coatings. Here, we reported an effective approach to enhance the graphene retention, and thus improve the performance of plasma-sprayed alumina/graphene nanoplatelets (Al₂O₃/GNPs) coatings by heat treatment of agglomerated Al₂O₃/GNPs powders. The effect of powder heat treatment on the microstructure, GNPs retention, and electrical conductivity of Al₂O₃/GNPs coatings were systematically investigated. The results indicated that, with the increase in the powder heat treatment temperature, the plasma-sprayed Al₂O₃/GNPs coatings exhibited decreased porosity and improved adhesive strength. Thermogravimetric analysis and Raman spectra results indicated that increased GNPs retention from 12.9% to 28.4%, and further to 37.4%, as well as decreased structural defects, were obtained for the AG, AG850, and AG1280 coatings, respectively, which were fabricated by using AG powders without heat treatment, powders heat-treated at 850 °C, and powders heat-treated at 1280 °C. Moreover, the electrical conductivities of AG, AG850, and AG1280 coatings exhibited 3 orders, 4 orders, and 7 orders of magnitude higher than that of Al₂O₃ coating, respectively. Powder heat treatment is considered to increase the melting degree of agglomerated alumina particles, eventually leaving less thermal energy for GNPs to burn; thus, a high retention amount and structural integrity of GNPs and significantly enhanced electrical conductivity were achieved for the plasma-sprayed Al₂O₃/GNPs coatings.

To extend the service life of sensors in seawater, this work prepared an integrated diffusion-plated Al₂O₃ film using high-power impulse magnetron sputtering (HiPIMS). The tribological properties of the Al₂O₃ film in a marine environment were tested using a tribometer. The morphology and evolution of the Al₂O₃ film before and after the friction tests were investigated by characterization techniques such as field emission scanning electron microscopy (FESEM). The results demonstrate that the Al₂O₃ film exhibits excellent tribological performance in the marine environment, significantly enhancing the wear resistance of the substrate material. Furthermore, with the protection of the Al₂O₃ film, the designed pressure sensor achieved high-sensitivity detection of minute operational forces underwater. When applied to a robotic gripper for manipulation tasks, the coated underwater sensor enabled accurate perception of subtle motion states of the grasped objects.

In this paper, a series of Co-free FeCr_0.6Ni_0.6(AlSi)_x (x = 0, 0.1, 0.12, 0.14, 0.16) high-entropy alloys (HEAs) were designed and fabricated by suction casting, and the effects of equi-molar (Al, Si) co-addition in these Fe-rich Fe-Cr-Ni-based HEAs on microstructure, mechanical properties, and corrosion resistance were systematically investigated. It is found that equi-molar (Al, Si) co-addition could cause the phase formation from FCC to FCC + BCC, while the morphologies of the phases change from dendrite-type to sideplate-type. Moreover, trade-off between strength and plasticity occurs with the increase in (Al, Si) co-addition, and the production of ultimate tensile strength and plasticity reaches the highest value when x = 0.12, while there exists a narrow region for x values to realize excellent comprehensive mechanical properties. In addition, similar corrosion resistance in 3.5 wt.% NaCl solution higher than 316L stainless steel could be realized in the HEAs with x = 0.12 and 0.14, while the latter one is slightly lower in pitting corrosion and the width of passive region, which is possibly caused by the increase in the density of phase boundaries. This work provides a novel insight on designing high-performance cost-effective Fe-rich and (Al, Si)-containing (Fe-Cr-Ni)-based HEAs combining high mechanical properties and corrosion resistance.