Adhesion strengths and microstructures of TiN coatings on white layer composed of ε nitride (Fe2-3N) were examined. In the present study a hot work tool steel, SKD61, was used for a substrate. The substrates were coated with TiN by physical vapor deposition (PVD). Specimens were prepared with changing the conditions for polishing the surface of the substrate, and conditions for nitriding before PVD treatment. Peeling of the coated film occurred on un-polished specimen surface. Other specimens can be coated with TiN film without peeling. The microstructures, phase identifications and adhesion strengths were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), scratch tester and Rockwell adhesion tester, respectively. The black layer formed between the TiN film and white layer was observed by SEM, which generally deteriorates adhesion strength. However the scratch tests showed that the adhesion strengths of the specimens with black layer were higher than those on the specimen without the black layer. The black layer would not always decrease the adhesion strength.
Metal silicides are potential materials because of their excellent properties such as corrosion resistance, oxidation resistance and wear resistance. In this study, the authors propose a new surface treatment process to form metal silicides on metallic materials by using an atmospheric controlled IH-FPP. Atmospheric controlled IH-FPP in which Si particles are bombarded to the substrate with an elevated temperature of 1173 K can form the iron silicide. Elevated temperature of the substrate enhances transfer of Si particles on the substrate, followed by mixing and/or diffusion into the substrate. This results in the formation of iron silicides. Atmospheric controlled IH-FPP with Si-Cr mixed particles also forms the iron silicide. Atmospheric controlled IH-FPP with the mixed particles followed by annealing of 873 K for 3600 s forms chromium silicide in accordance with Fe-Cr-Si ternary phase diagram. Carbon steel materials covered with the silicide layer exhibit better corrosion resistance since SiO2 is formed on the silicide.
In this report, the surface properties and microstructure of chromium-molybdenum steel samples prepared by two-stage gas nitriding with a short isothermal time in stage one are compared with those prepared by one-stage gas nitriding. Two-stage gas nitriding was performed with a short isothermal time in stage one followed by a second stage with lowered NH3 partial pressure. One-stage gas nitriding under conventional conditions was compared with it. The variation in microstructure, compound layer thickness (CL), nitrided case depth (d) and surface hardness (HVs) was clarified. In one-stage gas nitriding, the CL, d and HVs increase with increasing isothermal time. In contrast, in two-stage gas nitriding, the CL decreases with isothermal time in the second stage, and surface microstructure observations show partial dissipation of the compound layer. The d and HVs increase at a lower rate of increase than the values observed in one-stage gas nitriding. However, when the second stage temperature was increased in two-stage gas nitriding, the CL decreases and partially dissipates in a shorter time, and d increases at a faster rate than those observed for one-stage gas nitriding. The HVs exhibits a faster rate of increase in the second stage when a higher temperature was used, but the rate is lower than that observed in one-stage gas nitriding. These experimental results are briefly discussed in relation to the microstructure.
Attempts have been made to clarify polarization behavior of aluminum alloy 1050 in 30 mass%nitric acid solution which is in deaerated and stagnant solution condition. It is shown that the dissolution of aluminum behaves in the fast and like a general dissolution manner when the 1050 specimen was dipped into the solution. It was found that the corrosion rate of 0.25 mA·cm−2 obtained from the corrosion weight loss roughly corresponded to the current density of 0.29 mA·cm−2 on the assumption that the dissolution of aluminum in the nitric solution is categorized to electrochemical reaction of the fast system.
Light couples with free electrons in metals on the nanometer scale, exhibiting a localization and enhancement effect known as Localized Surface Plasmon Resonance (LSPR). LSPR has been exploited in many scientific and industrial fields, such as sensors, optical waveguides, high-sensitivity optical detection, high-resolution microscopy, etc. In spite of the versatility of LSPR, the applicable wavelength range of LSPR has been limited to the visible and infrared because the host materials for conventional LSPR, mainly gold and silver, do not exhibit metallic behavior at ultraviolet (UV) wavelengths. We used aluminum as a new candidate LSPR material at UV wavelengths and optimized its structure for better coupling with light from UV to deep-UV. Aluminum nanostructures were fabricated by a nanoparticle lithography method. In this report, we especially focus on the relationship between the LSPR wavelength and the height of the nanostructures. By increasing the height of the nanostructures, blue shifts of the LSPR wavelength were observed. With finer tuning of the nanostructures, an LSPR wavelength of 244 nm was successfully achieved, which is the shortest reported LSPR wavelength.