Analytical and electrochemical methods were used to study the dissolution behavior of annealed SUS 304 stainless steel in the descaling process in order to determine the annealing conditions needed to make scale easily descalable. The following conclusions are advanced: (1) With anodic electrolysis in 20% Na2SO4 solution (pH 3), oxides of Cr, Mn and Fe in the outer layer of the scale are dissolved relatively quickly, but Fe in the inner layer is dissolved at a considerably low rate. The amount of dissolved Fe increases markedly at a potential above 1.4V vs. SCE, which is nobler than that of Cr and Mn by 0.2∼0.3V. Cathodic electrolysis is of no use in dissolving these oxides. Si oxide in the inner layer of the scale is not dissolved by electrolysis in 20% Na2SO4 solution and obstructs the dissolution of other coexisting elements such as Cr and Fe, but it is dissolved by immersion in nitric-hydrofluoric acid. (2) To reduce the time required for descaling, it is important to lower the Si and Fe content in the scale and raise the Cr and Mn content, while making the scale thinner.
Transition metal nitrides have been used as corrosion resistant materials in recent years. To evaluate the corrosion resistance of iron nitride, iron nitride films having various compositions were produced by reactive ion plating. At a constant electron beam current the nitrogen content of the product film tended to increase as the flow rate of N2-H2 as the reactive gas increased. A decrease in the electron beam current used to evaporate the iron also led to an increase in the nitrogen content of the product film. X-ray diffraction showed that 7.3∼24.7 at % N nitride films had a mixed structure of α-Fe and γ′-Fe4N, while at 26.6 at % N the films were single phase ε-Fe3N. The amount of dissolved iron from the iron nitride film decreased with increasing nitrogen content. Corrosion of ε-Fe3N film was apparently inhibited in 1.0kmol·m-3 NaCl at 333K. For specimens with a mixed structure of α-Fe and γ′-Fe4N, corrosion occurred preferentially on α-Fe. It was presumed that a portion of the α-Fe dissolved as an anode and that in this solution the reaction proceeded via a chloride as an adsorbed intermediate.
A novel method was developed for the preparation of white fine powders coated with ITO. Fine powders, such as TiO2 and Al2O3, previously coated with hydorlyzed Sn(OH)4 film were homogeneously coated with a mixed hydroxide film of ITO composition by simultaneously adding a acidified metal chloride solution and ammonia water to maintain a suspension pH of around 7 at a temperature near 343K. After filtration and water rinsing, the powders were annealed at 773K for 1 hour to form a uniform ITO film. The range of the electro-conductivity of the prepared powders extended from several to tens Ω·cm. Well-coated ITO film exhibits sufficient resistivity to AGA grinding. Coupling agents, such as silane-type agents, remarkable effectiveness against aging deterioration the electro-conductivity of the powders.
In order to investigate the mechanical properties of ion-implanted Ti alloy (Ti-6Al-4V), disk samples of Ti-6Al-4V were implanted with 200keV N2+ ions at doses of 2.5×1016 to 5×1017 ions/cm2. Tribological properties were evaluated with pin-on-disk tests. Bearing steel (SUJ2) balls 5mm in diameter were used as pins. Sliding conditions were as follows: load, 0.46N; speed, 0.04m/s; oil lubrication, SAE 7.5W-30. Knoop hardness (load: 98mN) increased from Hk 356 to Hk 556 (dose: 5×1017ions/cm2) with ion dosage. The coefficient of friction of N2+ ion-implanted Ti-6Al-4V disks ranged from 0.1 to 0.2, values that were lower than 0.6 obtained for an unimplanted disk. N2+ ion implantation reduced wear on the pins as well as on the Ti-6Al-4V disks. The seizure load of N2+ ion-implanted disks increased with ion dosage.
The origins of nodule formation in electroless nickel-phosphorus deposition were investigated. It was found that the pretreatment and plating conditions influenced the formation of nodules. Nodules were observed in the fractographs of the depositions depending on changes in the surface morphology of the copper substrate when the plating baths included mono- or di- carboxylic acids. On the other hand, nodules were not observed in the fractographs of the depositions with plating baths that contained hydroxycarboxylic acids. Nodules tended to be less likely to form when the deposition rate was relatively low and the phosphorus content of the deposition was high.
This report describes the crystal structure of and heat-induced structural changes in electroless palladium plating films deposited from an ethylenediamine complex bath using trimethylamine borane as a reducing agent. The boron content of the films and their crystallinity were proportional to the concentration of trimethylamine borane in the bath. X-ray diffraction data showed a diffused pattern, in as-plated films (before heat-treatment), which changed into the sharp crystalline features of PdH0.706 at 400°C, and the sharp crystalline features of the Pd phase after heat-treatment at 600°C. The diffraction angle of the Pd phase shifted to a slightly lower angle following an increase in boron content.
Long-term atmospheric exposure of weathering steel coated with a phosphoric acid-iron oxide-PVB surface treatment for rust stabilization produces a dense, stable oxide layer. This layer is itself made up of an outer layer of rust, which includes a deteriorated treatment film, and an inner layer of rust, which is mainly amorphous rust. Artificial (magnetite) rust testing performed to investigate the effect of PO43- and Cu2+ on rust morphology showed that PO43- has a strong amorphization effect on rust and is especially effective in oxygen-deficient environments. Cu2+ also has a rust refinement effect in oxygen-deficient environments, although this effect is weaker than that of PO43-. From these results, it can be inferred that the amorphous rust underneath the treatment film is formed by an reaction between Fe2+ produced by an iron matrix corrosion and PO43- and Cu2+ that flow out from the treatment film in an oxygen-deficient environment. Furthermore, by acting to encourage the oxidation of Fe2+ to Fe3+, Cu2+ and PO43- have an effect of suppressing“rust outflow”
Despite thier thinness, films applied to weathering steel using a phosphoric acid-iron oxide-PVB rust stabilization surface treatment act to inhibit rust formation and to suppress“rust outflow”. The following conclusions were reached in a study of the reasons for the treatment's effectiveness. (1) The treatment film exhibits cation selectivity in a NaCl solution and KCl solution and anion selectivity in a FeCl2 solution and FeCl3 solution. Accordingly, by acting to suppress the diffusion of Cl-, Fe2+ and Fe3+, the film inhibits corrosion of the iron matrix and the occurrence of“rust out-flow”. (2) Examination of artificial rust (amorphous rust) revealed that a compound layer comprised of the treatment film and rust acts as a bipolar film with both cation selectivity and anion selectivity. The compound layer also suppresses the diffusion of Cl-, Fe2+ and Fe3+. (3) Because the treatment film has a relatively high permeability for moisture and oxygen, PO43- and other phosphate ions easily flow out of the film during prolonged atmospheric exposure. It is thought that PO43-, in addition to imparting ion selectivity to the rust, contributes, together with the alloying elements, to rust stabilization in weathering steel.
Silicon oxide film was deposited on a Si substrate by microwave (2.45GHz) plasma enhanced metal-organic chemical vapor deposition (PE-MOCVD) using hexamethyldisiloxane (HMDSO) as the silicon source, oxygen, and argon. The influence of the deposition temperature on the quality of the deposited film and on its deposition rate was investigated by means of FT-IR, XPS, and ellipsometry. In FT-IR measurement of the film, absorption bands from SiMex and/or Si-OH were observed as impurities in the low deposition temperature range (60-170°C), but these absorption bands disappeared at higher substrate temperatures (<170°C). Post plasma treatment of the deposited film using argon-oxygen plasma was also performed in an attempt to decrease impurities in the film, and as a result the SiMex band disappeared completely. In conclusion, MOCVD enhansed by microwave argon-oxygen plasma treatment proved to be in low temperature deposition of silicon oxide film from HMDSO.
Ever though fatigue in anodized coating on aluminum is on extremely important matter in aircraft, there have been few reports on the problem, so we studied the effect of the existence of anodic oxide film on aluminum using S-N curves determined by the rotational bending fatigue method. The following results were obtained; (1)The anodized coating fatigued easily on the high stress side, but not on the low stress side. On the high stress side, this was because a notching effect acted on the coating owing to the occurrence of cracks, while on the low stress side, the fatigue limit was greater than with no anodized coating because of the hardness of the oxide film. (2)The rupture planes were almost, but not perfectly, directly planer.