Materials Science Forum Vol. 844

Abstract: The thermal barrier coating that consisted of ZrO₂-8Y₂O₃ top-coat and Ni-22Cr-10Al-1Y bond-coat corroded in Ar-1%SO₂ gas at 1000-1200°C for up to 300 h. The top-coat and bond-coat consisted primarily of β-ZrO₂ and (γ-Ni, α-Al₂O₃), respectively. During corrosion, Al oxidized preferentially to α-Al₂O₃ to protect TBC, and sulfidation occurred to a small extent.

Abstract: The article studies results of corrosion-mechanical behavior of multifunctional composition "steel-material with a shape memory effect" formed in high-energy impacts in different environments. Analysis of experimental results shows an increased resistance to corrosion of the composition "steel-material with SME based on TiNi, NiAl» and confirms their protective properties in water, natural atmosphere, marine environments, saturated NaCl solution and medium aggressive environments. It has been shown that for highly corrosive acids with concentration of > 20% based on hydrofluoric HF, hydrochloric HCl, sulfuric H₂SO₄ there are several limitations and stages associated with dissolution of the layer and loss of corrosion resistance. Given the significant effect of surface treatment method on the whole range of functional and mechanical properties of materials with shape memory effect, we proposed recommendations on the selection of compromise solutions.

Abstract: The article contains analysis results of destruction of chemical generator corps representing thin-walled pressure vessels working under cyclic loading and in corrosive environments. It is shown that the corps made of steel 321 was destroyed mainly along the weld and heat affected zone. To improve the durability of corps we used materials with shape memory effect (SME) based on NiTi as alloying compound of welds. This allowed us to combine the functional properties of alloys with shape memory effect with increased mechanical, technological and operational properties. Accomplished electrochemical studies of corrosion behavior of steel 321 samples alloyed with NiTi in 3.5% NaCl solution, showed that the corrosion rate of welded joint and the base material are comparable. Fatigue tests in the environment KOH + H2 showed a significant reduction of ductility, which indicates the presence of hydrogen embrittlement. With increasing degree of hydrogenation the fatigue life of alloyed compounds drastically reduces.

Abstract: Abstract. Some features of behavior and kinetic of the anodic processes for the platinum and Cu–Fe–Ni alloy in the KF–NaF–AlF₃–Al₂O₃ melts at 1025–1055 K have been studied by cyclic voltammetry and chronopotentiometry.The obtained results allowed us to conclude that mechanisms of the anodic processes at the platinum and Cu–Fe–Ni alloy are similar. Both mechanisms include the oxidation stage of electrode material. A rate of this stage is determined to depend significantly on the melt temperature.

Abstract: To develop modern CAE systems for durable and reliable structure components design, mathematical modeling of environmentally assisted metal cracking becomes very important. For structure components exploited in aggressive environment and under cyclic load, it is a problem of today. Besides, mathematical rule of damage accumulation of different causes (for instance, hydrogen media impact and cycling) is rarely used in CAE systems, but if such rule was used, crack propagation simulation considering several damage causes would be possible.Environmentally assisted metal cracking model (developed earlier by authors) is described in the paper. This model considers cyclic load and hydrogen embrittlement, the most important characteristics of which are hydrogen environmental concentration and load frequency respectively.The authors’ model successfully predicts effect, known from certain experimental data, that the greater is the frequency, the less hydrogen embrittlement affects fatigue cracks propagation and, vice-versa, that there are certain boundaries of cycling frequency for which embrittlement effect is comparably big.Such boundaries of frequency were numerically estimated by means of the presented model. Plots showing dependency of the component’s life on different defect and loading features are shown.

Abstract: Corrosion rates of aluminum in phosphoric (V) acid solutions were determined gravimetrically in a presence of sodium molybdate which acts as an inhibitor. Inhibition efficiencies were calculated. The most effective corrosion inhibition was observed for 0.5 M H₃PO₄ and 100 mM of Na₂MoO₄. Since insoluble corrosion products precipitated onto specimens and influenced the determined corrosion rates, an analysis of a morphology of the specimens was performed by using a scanning electron microscope. The corrosion products are composed of Mo, P, Al and O. An Mo/P atomic ratio varied between 0.8 and 1.6 depending on the concentrations of phosphoric (V) acid and sodium molybdate. For three concentrations of H₃PO₄, the concentration ranges of sodium molybdate, where the gravimetric method may be applied were determined.

Abstract: The Al-brasses are considered corrosion resistant construction materials often used to pipe systems in energy industry, where they are exposed to flowing liquids environments. In that system the brasses are loaded chemically and mechanically. The aim of our research work is to compare corrosion properties of four Al-brasses produced by different manufactures because in operation conditions they have dissimilar reliability and durability. The examined Al-brasses have similar chemical composition but differ in microstructure, surface state what affects their corrosion and mechanical properties. The effect of the mentioned parameters on corrosion and mechanical susceptibility to degradation are investigated by chosen experimental methods.

Abstract: Fe-Mn alloys represent promising degradable biomaterials for temporary implants. To investigate the effect of corrosion on their mechanical properties, iron powders were mixed with 25, 30 and 35 wt.% of a manganese powder, compressed into prismatic bars and sintered. Sintered bars were immersed in Hank's solution for 8 weeks. The bending stiffness of each bar before and after its exposure to electrolyte was examined. The higher the porosity of a bar was, the higher relative reduction in bending stiffness the bar exhibited. A likely explanation was that in a more porous bar Hank’s solution penetrated deeper and affected larger volume fraction of bar’s material.

Abstract: Exploitation of ambulances in contaminated conditions causes that they are exposed to damaging the surfaces. Steel components are protected from corrosion by metallic and paint coatings, e.g. selected parts of medical equipment are protected by Ni, Cr, Cu coatings and additionally by hot-dip galvanizing or zinc galvanic. The appearance of corrosion cells has a significant impact on the products sustainability.In the study the results of the research, regarding the application of innovative solutions from the field of the material science and medicine in the interior of modern ambulances are described. The aim of investigations was the proper selection of anticorrosion coatings appropriate to ambulance considering the sterility keeping and the best anticorrosion properties.