In order to improve the biocompatibility of Ti-6Al-4V alloy, Ti-O coatings formed thereon by reactive DC sputtering in Ar-O2 mixtures, the oxygen contents of which were regulated by mixing the desired amount of oxygen into a constant flow of argon, were examined and the effects of oxygen flow rates were discussed. Under visual observation, all Ti-O coatings obtained appeared to exhibit good uniformity and adhesion, but under SEM their surfaces were found to have a duplex microstructure of fine particles dispersed on a smooth accumulated deposit. The Vickers hardness of the film increased almost linearly with increasing oxygen flow rate, and maximum hardness was more than Hv 1600. Under AES, the Ti/O ratio in the depth direction was nearly constant for all films, and their oxygen contents increased with increasing oxygen flow rate. Based on the results of X-ray diffraction, it was concluded that at lower oxygen flow rates, oxygen atoms dissolved into α-titanium crystals, while at higher rates suboxides such as Ti4O7 and Ti6O11, and oxides such as TiO2 (anatase) were formed.
Ti-C-N films were deposited as a TiN-TiC solid solution by a reactive ion plating system activated by arc discharge and were applied to side trimmers. Dependence of chemical composition of the coatings on properties such as hardness, oxidation resistance, residual stress, critical load and wear resistance were studied. The coatings exhibited extremely high hardness, and pin-on-disk tests on multilayered coatings revealed superior wear resistance against steels. It is suggested that fine iron debris comes from steel pins and is oxidized by the reaction with oxygen in air, and that a protective oxide particle can be formed by the growth of oxide debris on the hard surface. The tool-life of side trimmers was markedly improved by the application of the Ti-C-N coatings, due to the fact that multilayered Ti-C-N coatings decreased the sliding-wear rate of the side edge of side trimmers in shearing steel sheets.
Zn-Ni alloys were electrodeposited onto steel sheets from a sulfate bath containing zinc cation and nickel cation at duty cycles of 100, 90, 70, 50 and 20%. The Ni content of the deposits increased and cathodic current efficiency decreased with a decreasing in duty cycle. The surface morphology changed from granular to smooth and crystal structure changed from a mixture of Zn and Zn-Ni alloy phase to Zn-Ni alloy single phase with a decreasing in duty cycle. It was thought that these changes were attributed to the selective dissolution of zinc from deposits during offtimes and to the decrease in the thickness of the diffusion layer caused by galvanostatic pulse condition. Although internal plating stress increased with a decreasing in duty cycle, they reached a constant level after anodic dissolution in NaCl solution due to the occurrence of microcracks in the deposits. Corrosion protection properties increased with decreases in the duty cycle.
WO3/PPTA composite films consisting of poly (p-phenyleneterephthal amide) (PPTA) and tungsten (VI) oxide (WO3) were prepared by the same method described in a previous paper for PAn/PPTA films. Electrochemical, electrochromic and mechanical examinations revealed that WO3/PPTA films had virtually the same electrochemical and electrochromic properties as WO3 films, and much greater mechanical strength (tensile strength: 84 MPa, tensile modulus: 1.9GPa) and flexibility. It was also found that WO3 electrodeposited by this method was amorphous and in electrochromic behaviorhydrogen ions played an important role as doping and undoping species in aquous solution.
Magnesium thin films were prepared on cold-rolled steel substrates by vacuum evaporation and ion plating. The influence of argon gas pressure and substrate bias voltage on the crystal orientation and molphology of the films was characterized by X-ray diffraction and scanning electron micrography, respectively. The crystal orientation of magnesium thin films deposited at a high gas pressure of 7.3Pa exhibited (002) preferred orientation, regardless of the substrate bias voltage. With an increase in argon gas pressure, film morphology changed from columnar to granular, and surface crystal grain-size and film thickness decreased. The morphology and crystal orientation offilms depended not only on gas pressure but also on bias voltage, an increase in bias voltage having a similar effect to a decrease in gas pressure. The observed phenomena can be explained by the gas adsorption inhibition effect and the ion sputtering effect. The effect of the crystal orientation and morphology of the magnesium thin films on corrosion behavior was estimated by measuring anodic polarization curves in deaerated 3%NaCl solution. Mgnesium thin films that exhibited (002) preferred orientation and granular structure showed good corrosion resistance. It was confirmed that the corrosion resistance of magnesium thin film can be improved by controlling crystal orientation and morphology.
The process of electrodeposition of Ni-Mo-P alloys from ammoniacal citrate baths was studied with reference to the effects of cathodic current density, bath composition, temperature, pH and electrolytic aging on the chemical composition and structure of the deposits. The compositions yielding amorphous Ni-Mo-P alloy deposits were found and the corrosion behavior of the deposits was clarified by potentiodynamic polarization tests. The crystal structure of the deposits was determined by X-ray diffraction profiles.
During the last decade, high power lasers (more than 1kW) have been applied in a wide range of field such as cutting, welding, quenching, glazing, alloying, cladding and spraying. In these processes, absorbents are necessary for the effective utilization of the laser energy and elimination of the hazard of beam reflection. Graphite is the most widely used energy absorbent for CO2 lasers. This paper reports the advantages of boron nitride (hBN), which being used as a solid lubricant and as crucibles, as the CO2 laser energy absorbent. This has been verified by the quenching width and depth and the hardness of quenching texture of steel. This paper also reports that BN is useful auxiliary for the laser cladding of copper on steel; this cladding mechanism was investigated