•TiAl(Si)N coatings were deposited on Ti6Al4V by arc ion plating.•Oxidation behaviors of coated alloy were investigated at 650 °C and 750 °C in air.•At 650 °C oxidation resistance of the substrate was improved by all the coatings.•At 750 °C beneficial effects were maintained by TiAlSiN but not by TiAlN coatings.•The better performance of TiAlSiN coatings could be attributed to addition of Si.For improvement of the oxidation resistance of the titanium alloy, multi-layered Ti0.5Al0.5N/Ti0.7Al0.3N and monolayer Ti0.5Al0.5N, Ti0.5Al0.45Si0.05N, Ti0.6Al0.3Si0.1N were deposited on Ti6Al4V alloy by arc ion plating. The isothermal and cyclic oxidation behaviors of the coated alloy were investigated at 650 °C and 750 °C in air. At 650 °C the oxidation resistance of the substrate was significantly improved by all the coatings. At 750 °C, the beneficial effects were maintained by Ti0.6Al0.3Si0.1N and Ti0.5Al0.45Si0.05N but not by Ti0.5Al0.5N and Ti0.5Al0.5N/Ti0.7Al0.3N coatings. The TiAlSiN coating exhibited better oxidation resistance than the TiAlN coating could be attributed to Si addition eliminating defect formation in the TiAlN coating during the oxidation process.

Cyclic oxidation of nano-crystalline 304SS coating was compared with that of conventional, micro-crystalline 304SS in both dry and wet (10% H2O) air at 900 °C. The nanocrystalline alloys were prepared by direct current magnetron sputtering coating. Weight change kinetics were measured by continuous thermogravimetry. For micro-crystalline alloy in dry air, a small initial weight gain was followed by gradually increasing spallation. Addition of water vapour to air produced immediate spallation, and led to significant breakaway oxidation. Microstructural analyses revealed the formation of iron-rich oxides on the surface. The addition of water vapour also accelerated the development of internal oxidation in the form of fine spinel precipitates dispersed in the chromium depleted matrix. In contrast, nano-crystalline 304SS, underwent relatively rapid oxidation in the very early cycles of reaction, but then the reaction slowed down. No spallation was apparent in either gas. The weight gain was higher in wet air than in dry air. In both gases a dense and continuous chromium oxide layer was formed at the surface, together with other oxides distributed inside the coating layer. The effects of cyclic reaction, grain size and water vapour on the resistance of 304SS to breakaway oxidation are discussed.Highlights► Cyclic oxidation of nano-coated 304SS investigated using thermogravimetric analysis ► Nano-structure significantly improves cyclic oxidation resistance of the 304SS. ► Nano 304SS has good resistance to breakaway oxidation in wet air over 100 cycles.

The corrosion of metals or alloys under solid NaCl deposit in wet oxygen (water vapor and oxygen) at medium temperature 400–700°C causes serious damage and has received considerable attention in recent years. Series of mechanistic studies have revealed synergistic interactions between solid NaCl and water vapor, which accelerates the corrosion process. In addition, the overall corrosion process comprises both chemical reactions (oxidation) and electrochemical reactions and their mutual interactions depend on the system of interest. Interestingly, the wet oxygen environment was found to modify the reactions of the element Cr, which plays a useful role in corrosion protection in this special environment.

A single water monomer is known as a hard-to-observe molecule even in the presence of metal surfaces as supporting matrix. This review highlights effort in experimental characterizations and theoretical modeling of transition metals supported water monomers with attention given to its structure and bonding, together with the insights that we have provided into the bonding nature of the water-interactions by the newly employed projected PDOS (partial density of states) difference analysis, which is proved to be an effective tool to be elucidate such bonding nature. The general s-d hybridization and d-shell effect are summarized, and how these effects can be tuned by tailoring local surface configurations is discussed.

A novel antibacterial stainless steel (ASS) with martenstic microstructure has been recently developed, by controlled copper ion implantation, as a new functional material having broad-spectrum antibacterial properties. The electrochemical corrosion behavior of the ASS in 0.05 mol/L NaCl was assessed using linear polarization and electrochemical impedance spectroscopy (EIS) and compared with that of a conventional stainless steel (SS) without copper ion implantation. The ASS exhibited higher corrosion susceptibility in the chloride medium; with a more negative (active) corrosion potential, higher anodic current density and lower charge transfer and polarization resistance. This has been attributed to the occurrence of copper-catalyzed interfacial reactions. A functional tool, 3-D presentation of EIS data, has been employed in analyzing the electrochemical corrosion processes as well as probing complex interfacial phenomena.

Surface films of TiN and TiN/Ti were deposited on Ti6Al4V alloy by arc ion plating (AIP). Open-circuit potential, potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) were employed to investigate the corrosion performance of TiN and TiN/Ti films in Hank’s simulated body fluid at 37 °C and pH 7.4. Scanning electron microscopy (SEM) was used to study the surface morphology of the corroded samples after the potentiodynamic polarization tests. The results show that the TiN and the TiN/Ti films can provide effective protection for the Ti6Al4V substrate in Hank’s fluid, and the TiN/Ti composite film showed a corrosion resistance superior to that of the TiN film. The outer TiN layer of the composite film mainly acted as an efficient barrier to corrosion during short-term experiments. In contrast to the bare Ti6Al4V, no pitting was observed on the surface of the TiN and TiN/Ti films deposited on the bare alloy after potentiodynamic polarization.

The adsorption of an H2O molecule on Ni{111} has been investigated by density functional theory (DFT) calculations. In addition to the consensus between previously reported experimental data and our DFT results arrived at via the surface relaxation pattern, the electron work function and energy levels of a free H2O, as well as the adsorption energy, we have further presented a previously unrecognized electronic picture for the stable on-top adsorption, by analysis of projected density of states. We have provided clear evidence that the Ni 3p orbitals (pz and py), specifically the hybrid orbitals: 3pz −2pz, 3py−2pz, 3pz −2py, and 3py−2py, play crucial roles in the water bonding at the surface. Our results thus offer a new and inclusive understanding of the electronic nature, which is beyond the conventional model of 3a1−3pz and 3a1−3py interactions.

Vitreous enamel coating is a promising candidate as a high temperature protective coating for titanium (Ti)-based alloys due to its high thermo-chemical stability, compatibility, and matching thermal expansion coefficient to the substrates. Vitreous enamel coating is economically attractive because of its low cost and easy handling. The oxidation behavior of Ti6Al4V (at 700°C) and Ti–48Al (at 800–900°C), with and without the vitreous enamel coating exposed to air, are investigated in this article. The results show that the vitreous enamel coating could markedly protect the substrate (Ti6Al4V and Ti48Al) from oxidation at elevated temperatures. In comparison, the TiAlCr coating might not provide long-term protection for the Ti6Al4V alloys due to the heavy interfacial interdiffusion at high temperatures, although a protective Al2O3 scale could form at the initial oxidation stage. The vitreous enamel coating remains intact, uniform, compact, and adhesive to the substrate, however, with undetectable interfacial reaction after oxidation. It is also worth noting that some new phases form in the coating during oxidation at 900°C, although the protectiveness of the coating seems to be unaffected.