Dissipated damaging and degradation od steel properties of oil and gas pipelines

Тривала експлуатація нафтових та газових трубопроводів часто супроводжується втратою вихідних властивостей, що негативно впливає на подальшу роботоздатність трубопровідної мережі. В роботі на прикладі магістральних нафтових та газових трубопроводів, експлуатованих упродовж 28…40 років, показано роль розсіяної пошкодженості як окремої стадії деградації механічних та корозійно-механічних властивостей. Особлива увага приділена вивченню поведінки водню в металі як індикатора інтенсивності розсіяної пошкодженості.Long-term service of oil and gas pipelines is often accompanied by a loss of as-received properties that effects negatively on a further workability of pipelines network. The role of dissipated damaging, as a separate stage of materials degradation, in a change of its mechanical and corrosion-mechanical properties is considered in the work by the example of trunk oil and gas pipelines exploited during 28…40 years. The special attention is devoted to a study of hydrogen behaviour as indicator of an intensity of dissipated damaging

Corrosion degradation of steels of the lattice hyperboloid constructions

Досліджено корозійну тривкість та електрохімічну поведінку вуглецевих сталей експлуатованих понад 100 років сітчастих гіперболоїдних конструкцій (веж Шухова) та сучасної вуглецевої сталі у вихідному стані у 0,3% водному розчині NaCl. Встановлено, що вуглецева сталь Аджигольського маяка характеризується нижчою корозійною тривкістю порівняно з сучасною вуглецевою сталлю у вихідному стані та вуглецевою сталлю водонапірної вежі у Черкасах, що зумовлено тривалим впливом агресивного корозивного наводнювального середовища. Виявлено погіршення низки корозійно-електрохімічних характеристик сталі маяка внаслідок її експлуатаційної деградації – стаціонарного потенціалу, густини струму корозії та поляризаційного опору, які можуть виступати достатньо чутливими інформаційними ознаками експлуатаційної деградації сталі.A number of unique engineering monuments – the lattice towers created by outstanding engineer V.G. Shukhov have been preserved in Ukraine. Atmospheric corrosion is the main reason of the deterioration of their performance because the towers are made of carbon steel, which has insufficient corrosion resistance and they are not properly protected against corrosion. Therefore, the expertise of constructions corrosion damages, the establishment of corrosion peculiarities, the use of modern corrosion protection and corrosion monitoring are necessary for their conservation. The paper is devoted to studying the influence of long-term operation on corrosion resistance and electrochemical behavior of carbon steels of lattice hyperboloid towers in comparison with modern carbon steel in the initial state and detecting the informative features, which are sensitive to a change of a metal state due to long-term operation. The corrosion resistance and electrochemical behavior of carbon steels of the 100-year-old Shukhov lattice towers and modern carbon steel in the initial state in 0.3% NaCl aqueous solution have been investigated. It has been established that the Adziogol Lighthouse carbon steel is characterized by the reduced corrosion resistance in comparison with the modern carbon steel in the initial state and the carbon steel of the Cherkasy water tower which is likely to be caused by long-term exposure to aggressive corrosive and hydrogenating environment. The deterioration of corrosion and electrochemical properties of lighthouse steel, such as stationary potential, corrosion current density and polarization resistance, due to its exploited degradation has been found. These characteristics may be enough informative features of the in-service steel degradation. To maintain a conservation of the lattice tower constructions it is necessary to provide its effective corrosion protection using modern technology

Specific features of deformation of the nitinol alloy after electrolytic hydrogenation

Specific features of the effect of hydrogenation on the susceptibility of a Ni–Ti alloy with shape memory to deformation are determined with the use of metallographic, electrochemical, and mechanical studies. Three sections are detected in the tensile curves of the specimens of nickel–titanium alloy in the initial state. The first section is linear due to the elastic deformation of the alloy with initial austenitic struc-ture. The second section is nonlinear and associated with pseudoelastic structural transformations of the original austenitic structure into a martensitic structure. The third section is also linear and caused by the elastic deformation of martensite formed in the course of deformation of austenite. After hydro-genation of the Ni–Ti alloy, the pseudoelastic structural transformation starts at a somewhat lower level of stresses than without hydrogenation. In this case, the specimens are destroyed after the termination of this transformation for a much lower level of plasticity than in the nonhydrogenated alloy. It is assumed that the electrolytic hydrogenation of the alloy promotes the formation of a very brittle hydride phase on the surface of Ti-type inclusions revealed in the structure of alloy in the initial state. Its thickness is determined by the duration of the process of hydrogenation rather than by the current used for hydro-genation

Peculiarities of assessing the degradation of structural steels under the action of cyclic loading and environments

Long-term operation of structural steels often intensifies their degradation, which manifests itself in a decrease in initial physical and mechanical properties. The work highlights the peculiarities of the steel degradation process and its assessment under conditions of cyclic loading, as well as under the action of corrosive hydrogenating environments. Special attention is paid to the role of in-bulk dissipated damage in the metal degradatio

Effect of Hydrogenation on Fracture Mode of a Reactor Pressure Vessel Steel

The conditions for hydrogen-induced intergranular fracture in an artificially embrittled, low-alloyed reactor pressure vessel were investigated using fracture toughness and stress corrosion cracking tests. The specimens were taken from two locations: the heat affected zone beneath the cladding and the base material directly below the heat-affected zone. A hydrogenating system allowed the tests to be carried out on both pre-hydrogenated specimens or with continuous hydrogenation during testing itself. Overall the results demonstrate a detrimental effect of hydrogen on sub-critical crack growth resistance of both materials. At 120¿C (close to the upper shelf) it led to a lower energy ductile fracture mode and isolated instances of transgranular fracture. At ambient temperature (in the ductile to brittle transition regime) some mixed intergranular and transgranular sub-critical crack growth was observed.JRC.DG.F.8-Renewable Energy (Ispra