Specific features of the oxidation of complex titanium alloys in the as-cast and recrystallized states

We study the heat resistance of complex titanium alloys with 4.5–11 wt.% Al in the as-cast and recrystallized states at a temperature of 800°C for 50 h. It is shown that the procedure of alloying has the same influence on the as-cast and recrystallized metals, and the initial structure affects the kinetics of oxidation of the latter. In this case, the ground recrystallized structure promotes the formation of oxide films with high adhesive strength guaranteeing high levels of the heat resistance of the alloy for long periods of holding. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 3, pp. 112–117, May–June, 2008.     

Plasma electrolytic ceramic-like aluminum oxide coatings on iron

The process characteristics of plasma-assisted electrochemical treatment of iron in aluminate electrolyte consisted of aqueous 0.1 M NaAlO₂ + 0.05 M NaOH have been studied. It has been shown that in the range of DC voltages from 260 to 340 V, it is possible to deposit dense ceramic-like coatings with the thickness increased from 0.3–0.5 μm after 1 min deposition time to 25–30 μm for 1 h of deposition. The coatings were examined by X-ray diffractometry, Fourier-transformed infrared, X-ray photoelectron spectroscopy, scanning electron microscopy, and an electrochemical potentiodynamic voltammetry. It is shown that in pre-spark conditions (100–200 V) and on the initial stages of micro-arc anodizing the forming films contain, along with amorphous aluminum oxide/hydroxide, a substantial amount of iron oxide/hydroxide. The coatings obtained by micro-arc anodizing at 260–360 V for 10–60 min represent amorphous aluminum oxide with inclusions of crystalline corundum phase. The films with a thickness of 4–15 μm deposited at the anodizing voltage of 320–360 V exhibited the uniformity and good corrosion protection properties after sealing with common agents.     

Influence of tin on the structure and properties of as-cast Ti-rich Ti–Si alloys

By the methods of DTA, X-ray diffraction, metallography and microprobe analysis, phase equilibria in the Ti-corner (more than 50 at.% Ti) of the Ti–Si–Sn system were studied. The solidus projection and the melting diagram (solidus+liquidus) were constructed. A new ternary compound T of composition Ti₅Si_1.2–1.6Sn_1.8–1.4 was found to form with the crystal structure of W₅Si₃-type. The ternary eutectic equilibrium L↔β-Ti+Ti₅Si₃+Ti₃Sn was established to occur at 1460 °C with the composition of the invariant point E at 77Ti–9Si–14Sn. Microhardness measurements were carried out for the primary grains of the alloys with 5 at.% Si.     

Structural state of powders of high-speed tool steels produced by shock-centrifugal spraying

Translated from Poroshkovaya Metallurgiya, No. 12, pp. 6–10, December, 1990.     

Photoelectrochemical oxidation of sulphur dioxide on a polyaniline-modified n-Si/ITO electrode

Surface modification of n-Si/indium tin oxide electrode by photoelectrochemically grown polyaniline film has been shown to result in the dramatic increase in the efficiency of the photoelectrochemical oxidation of SO₂ to SO₄²⁻ in acid medium.     

The preparation of PbO2 coatings on reticulated vitreous carbon for the electro-oxidation of organic pollutants

The preparation of PbO₂ coatings on reticulated vitreous carbon (RVC) has been carried out at constant current from electrolytic baths containing aqueous Pb(II) and methanesulfonic acid (MSA, CH₃SO₃H). The morphological and structural analysis of the RVC/PbO₂ deposits carried out by scanning electron microscopy (SEM) and X-ray diffraction revealed that a thick (100 μm), homogeneous, nanostructured β-PbO₂ film can be successfully formed. As a result, three-dimensional β-PbO₂ structures were obtained, being particularly interesting for their use as anodes in wastewater treatment. The high oxidation ability of these anodes has been verified by the electro-oxidation of Methyl Orange aqueous solutions. Quick decolourisation was achieved, with total colour removal in less than 60 min at 600 mA due to the production of large amounts of reactive OH radicals from the oxidation of water at high anodic potentials. The progressive mineralisation of the solutions was also ascertained from the total organic carbon (TOC) removal, which was much quicker at a higher applied current. All the coated RVC electrodes exhibited excellent long-term stability and remained unaltered after prolonged electrolyses. In addition, novel PbO₂ composite coatings were prepared in the presence of hydrothermally synthesized titanate nanotubes (TiNT). The SEM images showed the presence of TiNT agglomerates along the PbO₂ surface, which led to higher anodic current in the cyclic voltammetries carried out with Methyl Orange solutions. It is suggested that TiNT favour the adsorption of the organic molecules, facilitating the contact with the OH radicals and thus accelerating the electro-oxidation process. This was confirmed by the faster TOC removal compared to that yielded by the RVC/PbO₂, being 45% instead of 24% at 120 min.     

Unique features in the characteristics of friction and wear for materials based on high-speed steel

Translated from Poroshkovaya Metallurgiya, No. 12 (348), pp. 68–71, December, 1991.     

Permeable materials of fiberlike rapidly hardened particles

Translated from Poroshkovaya Metallurgiya, No. 12 (348), pp. 26–29, December, 1991.