Oxidation of ferritic steels dispersion strengthened with TiO2 and Y2O3 oxides in lead melt

We study the structure and composition of scales formed during the contact of Fe–13Cr–2Motype ferritic steels hardened with oxides TiO₂ and Y₂O₃ with oxygen-containing (10⁻³ mass% O) lead melt at 550°C for 1000 h. It is established that a Fe₃ O₄ – Fe (Fe_{1 − x} , Cr _x )₂ O₄ two-layer scale forms. Its upper layer (Fe₃ O₄) grows in the direction of the melt, and the internal layer (Fe (Fe_{1 – x} , Cr _x )₂ O₄) grows in the direction to the matrix. Oxide particles favor an increase in the porosity of the internal sublayer of the scale. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 5, pp. 38 – 44, September–October, 2008.     

Interaction of Solid Metals with Melts Containing Nonmetallic Impurities

We present a systematic survey of the mechanisms of interaction of solid metals (Me) with melts (L) taking into account the activity of nonmetallic impurities (I) and suggest a general scheme of interaction of components in Me–L–I systems. The physicochemical aspects of formation of different layers on the Me–L phase boundary are analyzed. Special attention is given to the conditions of formation of protective layers with various functional properties. It is shown that this problem can be solved theoretically within the framework of the problem of reaction-controlled diffusion by taking into account the behavior of the concentrations of the components on the phase boundaries.     

Effect of temperature on the interaction of ÉP823 steel with lead melts saturated with oxygen

We study the corrosion behavior of ferritic-martensitic éP823 steel in a static lead melt, saturated with oxygen, at 550 and 650°C. At these temperatures, a complex magnetite-base scale is formed on the surface of steel, but the mechanisms of its growth are different. At 550°C, corrosion has a cyclic character. On the surface of steel, a Fe_1+x Pb_2−x O₄−Fe_1+x Cr_2−x O₄ two-layer scale is formed periodically. Reaching the critical thickness (18 μm), it exfoliates along the interface with the matrix, to which oxygen-containing lead penetrates, whereupon this process is repeated. The corrosion rate is ∼0.08 mm/year. At 650°C, the intensification of reactions of formation of chromium spinel and plumboferrite induces the growth of a porous scale, where lead is accumulated. This scale has good adherence to the matrix and is formed as a compact conglomerate owing to the efficient mass transfer at all interfaces, which leads to a catastrophic rate of thinning of the specimen (3.82 mm/yr) in a lead melt. On the basis of experimental data, we propose schemes of the oxidation of chromium steels in a lead melt with a high oxygen activity at different temperatures. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 2, pp. 77–84, March–April, 2007.     

Influence of the surface mechanical pulsed treatment on the oxidation of Fe – 0.2C – 13Cr – 0.3Si steel in lead melts

We study the influence of mechanical pulsed treatment (MPT-1) on the corrosion resistance of Fe – 0.2C – 13Cr – 0.3Si steel in a lead melt containing 1.3 · 10^{– 3} wt.% of oxygen at a temperature of 550°C for 1000 h. It is shown that the MPT promotes the formation of micro- and macrodefects in the subsurface zone of the specimens, which intensifies the process of oxidation of steel. The oxidation resistance of steel after MPT-2 and MPT-3 (with adding aluminum and silicon) is attained as a result of the formation of a hardened zone with nanocrystalline structure and large lengths of grain boundaries intensifying the diffusion of chromium into the oxide films.     

Corrosion of 20Kh13 steel in lead melts saturated with oxygen

We study the high-temperature interaction (650°C, 500 h) of 20Kh13 chromium steel with melts of stagnant lead saturated with oxygen (C _{O [Pb]} ≈ 6 · 10⁻³ wt.%). First (up to 200 h), separate islands of Me₃O₄ oxides (Me: Fe, Cr, Pb) are formed on the steel surface. In the course of time (for 500 h), these islands completely cover the steel surface as a result of lateral growth. The upper part of the oxide layer is formed by the (Fe_{1 − x} Pb_x) O · Fe₂ O₃ complex oxide growing from the initial “solid-metal—melt” interface toward the liquid-metal medium. The inner part of the oxide layer is spinel [(Fe_{1 − x} Pb_x) O · (Fe_{1 − y} Cr_y)₂O₃] enriched with chromium and formed on the basis of the matrix. Both layers symmetrically grow with respect to the initial “solid-metal—melt” interface. Lead does not penetrate into the steel matrix and is fixed only in the oxide layer. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 5, pp. 36–40, September–October, 2005.     

Compatibility of reduced activation ferritic martensitic steel JLF-1 with liquid metals Li and Pb–17Li

The corrosion of reduced activation ferritic martensitic steel, JLF-1 (Fe–9Cr–2W–0.1C), in high-purity Li was quite small. However, carbon in the steel matrix was depleted by the immersion to the Li. The depletion caused the phase transformation of the steel surface in which the morphology of the steel surface changed to ferrite structure from initial martensite structure. The phase transformation degraded the mechanical property of the steel. However, the carbon depletion and the phase transformation of the steel were suppressed in carbon doped Li. The carbon in the steel was chemically stable and did not dissolve into the Li when the carbon potential in the Li was high. The concentration of nitrogen and oxygen must be kept as low as possible because the corrosion was larger when the concentration of oxygen or nitrogen in the Li was higher. The chemical reaction between the steel and the Li compounds of Li₃N and Li₂O was also investigated. The corrosion of the JLF-1 steel in Pb–17Li was summarized as the dissolution of Fe and Cr from the steel into the melt. The corrosion of the specimen with Er₂O₃ coating fabricated by metal organic decomposition process in the Li and the Pb–17Li was investigated. The coating was deformed, cracked and partially exfoliated in the liquid metals, though the oxide itself was chemically stable in the liquid breeders. The damage was probably made by the stress, which was generated by a large difference of the thermal expansion ratio between the solidified Li or Pb–17Li and the coating during a heat up and a cool down process of the corrosion test.     

On dislocation mechanism of dynamic deformation of uranium

In this work, based on results of the tests with study of dynamic diagrams of compression of uranium-molybdenum alloy, we made an attempt to determine dislocation velocity, length of free run of dislocations, and increase of dislocation density during plastic deformation of alloy at dynamic strain rates.