Papers by Keyword: Hydrogen Degradation

Abstract: The work carried out complex and systematic studies based on of which the causes of accidental destruction of reinforcement of reinforced concrete structures of hydraulic structures is established, which is that corrosion damage to metal reinforcement is accompanied by its active flooding and embrittlement, resulting in reduced material properties against corrosion and mechanical destruction of reinforced concrete structures, especially after 20-40 years of operation. Based on existing approaches to the assessment of ageing equipment, developed in various branches of mechanical engineering, including the construction industry, identified trends and shortcomings in determining the efficiency of metal structures and their residual life, in connection with which the calculation and experimental methods of using the criteria of crack resistance, sensitive to changes in the structure of the metal during long-term operation. It is established that the decrease in crack resistance characteristics in the surface layers of reinforcement of reinforced concrete structures in contact with the aggressive environment is caused by the degrading effect of hydrogen on the crystal structure of the metal. The calculated-experimental method is offered, allowing to carry out engineering forecast estimation of residual (working) resource of the reinforced concrete designs operated in corrosive-aggressive environments of hydraulic engineering constructions, which adequately reflects physical and mechanical processes in metal which occur during its long operation.

Abstract: The aim of this work was to investigate whether the low alloy steel and the explosively welded metals used for salt caverns equipment's are susceptible to hydrogen degradation. The materials described in this article are cheap and widely used 09G2S low alloy steel and titanium grade1 as a clad material for its superior resistance to corrosive environment joined explosively with low alloy steel S355J2+N. It was observed that at the explosive bonded interface between the base steel and the stainless steel some local melting zones are formed. It was found that the cathodic hydrogen charging causes changes in the microstructure of low alloy steel and decreases the shear strength of bonds and tensile stress as well as the corrosion resistance of clads.

Abstract: The aim of this work was to investigate whether the explosively welded metals are susceptible to hydrogen degradation. The materials described in this article are widely used nickel alloy Inconel C-276 and super duplex steel SAF 2507 as clad materials for their superior resistance to corrosive environment and low alloy steel P355NH as a base material. It was observed that at the explosive bonded interface between the base steel and the stainless steel some local melting zones are formed. It was found that the cathodic hydrogen charging causes changes in the microstructure of bonded materials and decreases the shear strength of bonds as well as the corrosion resistance of clads.

Abstract: The paper presents results of research undertaken to determine the influence of hydrogen on passivity and corrosion resistance of 2507 super duplex stainless steel welded joints. Butt welded joints were made with low heat input using flux corded arc welding (FCAW) method. Coupons of 5.0 x 5.0 mm were cut from the welded joints containing weld metal (WM), heat affected zone (HAZ) and parent metal (PM). Hydrogen was introduced into the samples by cathodic current method under galvanostatic condition at room temperature. Corrosion resistance was qualified with the polarization curves registered in synthetic sea water. Electrochemical hydrogen charging affected the native passive layer. The internal hydrogen shifted corrosion potential to the more active direction and cause an increase in corrosion current density. The corrosion sensitivity increases for higher current density applied during hydrogen charging. Weld metal area has been revealed as the most sensitive to corrosion attack.

Abstract: Purpose of this paper is presentation of forms of hydrogen degradation in steel along with pointing out methods for hydrogen degradation prevention. The paper outlines influence of nitrided layer on 34CrAlNi7-10 steel to its susceptibility to hydrogen degradation. Investigation was carried out with the use of slow strain tensile rate test (SSRT). Fracture surfaces after SSRT test were examined with scanning electron microscope (SEM) to reveal a mode and mechanism of cracking.

Abstract: In this paper, the results are presented of the ultrasonic investigations of hydrogen degradation of 09G2S carbon steel. Samples of the steel were hydrogen charged with simultaneous registration of the ultrasonic signal. The results of ultrasonic investigations were verified by Light Microscopy (LM), Scanning Electron Microscopy (SEM) and X-ray microanalysis technique (EDS). It was shown that the in-situ ultrasonic flaw detection can be used to monitor the early stages of hydrogen degradation, i.e. the formation of microcracks caused by hydrogen trapping at nonmetallic inclusions and hydrogen blistering.