The hydrogen embrittlement susceptibility of electron beam melted Ti-6Al-4V alloy (ET) was compared with that of conventional wrought alloy (WT). Hydrogen permeation, electrochemical, and slow strain rate tensile tests as well as surface observation were conducted under a simulated sea environment. The results show that the hydrogen embrittlement susceptibility of ET is lower than that of WT, which can be attributed to the intense texture of ET with a smaller specific surface area of grain boundary, preventing hydrogen permeation. Moreover, with increasing depth of the ocean, the hydrogen embrittlement susceptibility of both ET and WT TC4 alloys increases considerably. This reduced hydrogen embrittlement resistance can be attributed to the degradation of the passivation film, accelerating the permeation flux of hydrogen.

The erosion–corrosion behavior of 90/10 and 70/30 copper–nickel tubes was investigated by in situ electrochemical tests on a self-built loop apparatus and ex situ surface characterization. The corrosion product film that formed at 1.5 m/s for the 90/10 tube and at 0.5 m/s for the 70/30 tube showed the best corrosion resistance. For the 90/10 tube, a continuous film existed below 3 m/s and mainly inhibited a cathodic reaction. For the 70/30 tube, a continuous film existed in the range of 0.5–4.7 m/s and was more similar to typical passive film electrochemically, although it was cracked at 4–4.7 m/s. So, the “critical flow velocity” of the 90/10 tube was between 3 m/s and 4 m/s, and that of the 70/30 tube was beyond 4.7 m/s.

Corrosion of 90Cu-10Ni alloy is related to oxide film formed in seawater. We characterize the initial oxides formed on different grains immersed in alkaline NaCl solution and reveal grain-orientation dependent Cu2O formation rate of (001) < (101) < (111) which causes Volta potential reversal among grains. We also implement the first-principles calculation on (001), (101) and (111) surfaces with monoatomic steps and demonstrate that anisotropic Cl adsorbing capacity and Cu dissolving capacity are responsible for different oxidation rates. Our results provide insights to optimize corrosion properties of conventional alloys on the concept of homogenizing oxide film by tailoring surface texture.

Hydrophobic coatings based on organic or ceramic materials usually suffer from low wear resistance and poor thermal stability, which limit their practical applications. Here we report a robust, hydrophobic CeO2/NiCoCrAlY composite coating prepared by air plasma spraying (APS), which shows superior wear resistance, excellent high-temperature stability and high bonding strength with the substrate. The coating can maintain its hydrophobicity after abrasion under 10 kPa over a 4 m distance, or after annealing at 773 K for 8 h. It also presents good corrosion resistance to protect the metallic substrate under corrosive working conditions. The CeO2/NiCoCrAlY composite coating provides a reliable and effective route to fabricate hydrophobic surfaces which may have potential applications in harsh environments. (C) 2021 Elsevier B.V. All rights reserved.

In this contribution, the ZrO2-doped YTaO4 (ZrxY0.5-x/2Ta0.5-x/2O2 (x = 0, 0.1, 0.2, 0.28)) are proposed as potential CMAS-resistant materials for TBCs. The corrosion behavior of those materials under CMAS attack are investigated from thermodynamics and kinetics. The results show that all compositions have the much better CMAS resistance than the classical Gd2Zr2O7. After 50 h corrosion at 1300celcius, the corrosion depth in ZrO2-doped YTaO4 bulks is about 50-80 mu m (for a 20 mg/cm(2) CMAS deposition) in contrast with similar to 140 mu m in Gd2Zr2O7 bulk. The CMAS corrosion mechanism of ZrO2-doped YTaO4 is elucidated, and the excellent CMAS resistance is attributed to the rapid formation and followed thickening of dense reaction product layer. Furthermore, the effects of ZrO2 doping content on CMAS resistance of YTaO4 is discussed. It is elucidated that ZrO2 doping can inhibit the precipitation of apatite, decrease the consumption of CMAS melt, and change the morphology of dense reaction layer. In summary, minor doping of ZrO2 can ensure the excellent short- and long-term CMAS resistance, but heavy doping of ZrO2 will degrade the long-term CMAS resistance.

Hydrophobic coatings are widely used in many areas from home to industry. However, the hydrophobicity can be easily degraded by adsorption of the atmospheric contaminations. In this study, a novel CeO2/black TiO2 hydrophobic coating with self-recovery capability is prepared using air plasma spraying without any chemical modification. The water contact angles (WCAs) of the coatings decreased after oleic acid contamination. Because of the presence of black TiO2, the composite coating has the photodegradation property under irradiation of visible light, and the part of the black TiO2 transforms to be superhydrophilic after irradiation for the generation of the surface oxygen vacancies. The oleic acid was decomposed and the WCAs changed depending on the volume percentage of the CeO2. The coating exhibits hydrophilicity when the volume percentage of the CeO2 is less than 60%, and hydrophobic when higher. After storage in a dark and clean environment, all the coatings can recover their hydrophobicity for the black TiO2 that returned back to its origin state. It is believed that this hydrophobic self-cleaning ceramic coating should have potential in engineering applications.

Hydrophobic coatings that could survive in harsh environment have a wide range of applications from industry to houseware. However, the state-of-the-art polymer-based coatings cannot meet such requirements due to their low melting point and poor wear resistance. In this study, we reported a plasma sprayed ceramic coating made of ceria with exceptional hydrophobicity, high-temperature stability, and good wear resistance. The coating exhibited a water contact angle (WCA) up to 139 degrees, due to the intrinsic hydrophobicity of ceria and unique surface morphology produced by plasma spraying. The WCA only slightly decreased to 131 degrees after annealing at 773 K. In addition, the polished coating (WCA similar to 116 degrees) was still more hydrophobic than the sintered bulk specimen (WCA similar to 95 degrees) with the same composition and roughness, which can be attributed to the surface chemistry change induced by Ar+ ion bombing by plasma. It is believed that such robust hydrophobic coating should have great potential in engineering application.