Papers by Keyword: Stress Corrosion Cracking

Abstract: The complex research of influence of a structural condition of metal on resistance to corrosion destruction of the low-alloyed steel, operated in biocorrosion environments, is conducted. It is established that the ferritic component of a structure resists better in the environment modeling conditions of impact of biogenous gases on metal under the exfoliated anticorrosive covering. Ferrite – carbide mix, in the form of beynit, has a bigger resistance in the environment reproducing conditions of lack of biogenous factors. Existence in beynitny structure of a martensitic component leads to the largest resistance of biocorrosion in the environment modeling conditions of anaerobic corrosion with biogenous gases.

Abstract: This chapter describes the cracking of stainless steel piping under Inter-granular Stress Corrosion Cracking (IGSCC) conditions using probabilistic fracture mechanics that predict the impact of in-service inspection (ISI) programs on the reliability of specific nuclear piping systems that have failed in service. The IGSCC is characterized by a single damage parameter, which depends on residual stresses, environmental conditions, and the degree of sensitization. The Probability of Detection (POD) curves and the benefits of in-service inspection in order to reduce the probability of the leak for nuclear piping systems subjected to IGSCC were discussed. The results show that an effective ISI requires a suitable combination of crack detection and inspection schedule. An augmented inspection schedule is recurred for piping with fast-growing crack to ensure that the inspection is done before the cracks reach critical sizes and that the use of a better inspection procedure can be more effective than a tenfold increase in the number of inspections of inferior quality.

Abstract: Quasi-cleavage facets have been detected in the stress corrosion cracking fracture of type 304 and type 316 austenitic stainless steels under an environment containing chloride. Their morphology and crystal orientation were analyzed. In both steels the cold-worked material (CW) showed higher crack propagation rate than annealed one (ST), where the variation of the propagated crystal planes of the CW was higher than that of the ST, and the {111} facet was detected in the CW. Then the CW reveals higher possibilities to choose a low energy crack path rather than the ST. The rearrangement and multiply of {111} dislocation arrays may introduce the {111} transgranular cracking in the CW, and the combining duplex {111} slip operations may result in the {110} facet.

Abstract: Four model alloys of the Fe-Cr-Co system have been tested under elongation at a standart rate and under pure bending with a constant load in air and in a corrosive medium after different treatment. Fractographic studies were performed depending on the cobalt content and duration of thermal aging at 450 °C. The experiment results are that the Fe-Cr-Co-based alloys with 5–10 % of cobalt are an acceptable composition for maraging steels since they have high strength and ductility, as well as corrosion resistance and low sensitivity to stress corrosion cracking.

Abstract: The 110 Ksi tubing failed in use when reservoir acidification reconstruction and production testing were performed in an oil well, which were longitudinal cracking of coupling. Failure analysis was conducted on the coupling. The failure zone was studied by means of macroscopic analysis, metallographic, scanning electronic microscope,energy dispersive spectrometer and X-ray diffraction analysis etc. The results indicated that the failure of the coupling is caused by stress corrosion cracking (SCC). SCC initiated from the exterior surface of coupling and displayed the fracture feature of intergranular crack propagation. The corrosion products at the grain boundaries were found to be mainly some oxides. The failure was in connection with the completion fluid composition, which are mainly nitrates.

Abstract: Cost factors must be considered in the development of Yan'an gas field. In order to evaluate the applicability of economical 80S steel in the sulfur gas reservoir environment of Yan'an gas field, the indoor corrosion test was conducted to evaluate the resistance of 80S steel to uniform corrosion and SCC resistance in CO₂/H₂S coexisting corrosion environment, and combined with relevant standards. The security was analyzed. The results show that the uniform corrosion rate of 80S steel is the largest at 50 °C, and it decreases first and then increases with the increase of temperature. When the loading stress is 496.8MPa (552MPa×90%),the test duration was 720h. One sample cracked and the other two parallel samples did not cracked Comprehensive anti-uniform corrosion performance and anti-SCC performance, it is believed that 80S steel has certain risks in the corrosive environment of Yan'an gas field. It needs to cooperate with other anti-corrosion measures and monitor the service of the well string at any time.

Abstract: The corrosion resistance of P110S steel in CO₂ and H₂S coexistence corrosion environment under different temperature and P_CO2/P_H2S was investigated by high temperature and high pressure (HTHP) reaction kettle combined with SEM, EDS and XRD analysis methods. The stress corrosion cracking (SCC) resistance of P110S steel was studied under loading pressure of 682.2MPa (758MPa×90%) in simulated conditions after 720 hours test. The results show that the P110S steel has serious corrosion in the range of simulative temperature and H₂S partial pressure. With the increase of temperature, the corrosion rate decreases first and then increases. With the increase of H₂S partial pressure, the corrosion rate increases first and then decreases. The P110S steel has the highest corrosion rate when the temperature is 50 °C and H₂S partial pressure is 0.1%. After the anti-SCC test, the specimens did not fracture, and cracks perpendicular to the tensile stress were not found on the surface. That is, P110S has good SCC resistance in the corrosive environment.

Abstract: The aim of this work is to better understand the evolution of the mechanical fields in cross-shaped specimens used to study the stress corrosion cracking (SCC) susceptibility of cold-worked stainless steels exposed to the primary water of nuclear power plants. Cross-shaped specimens are used since a loading path change leads to more severe cracking than a monotonous loading. During SCC tests, only the applied load and displacement can be measured as a result of experimental equipment limitations. Therefore, a mechanical test is performed ex-situ under similar condition as the ones applied during the SCC tests. The experimental deformation fields are measured by digital image correlation (DIC) and a numerical model is developed with ABAQUS to calculate the mechanical fields. The obtained results will allow us to calibrate SCC tests already performed but also to know the experimental boundary conditions to apply to reach a given strain value during forthcoming SCC tests.

Abstract: In this contribution, we propose a cohesive grain-boundary model for hydrogen-assisted inter-granular stress corrosion cracking at the grain-scale in 3D polycrystalline aggregates. The inter-granular strength is degraded by the presence of hydrogen and this is accounted for by employing traction-separation laws directly depending on hydrogen concentration, whose diffusion is represented at this stage through simplified phenomenological relationships. The main feature of the model is that all the relevant mechanical fields are represented in terms of grain-boundary variables only, which couples particularly well with the employment of traction-separation laws.

Abstract: The effects of chloride ion concentration on SCC susceptibility of 15Cr and 13Cr martensitic stainless steels were investigated at 180°C by SSRT. Transgranular SCC occurred in the environment containing CO₂ and chloride ion. The increasing chloride ion concentration was significantly affected SCC susceptibility of 15Cr SS. In addition, the contribution of hydrogen to SCC was examined at high temperature by SSRT with electrochemically polarization. The cathodically charged specimens showed hydrogen embrittlement. The fracture surface was similar to that of high temperature SCC. On the other hand, the SCC was accelerated by anodic polarization and not by cathodic polarization. The SCC behavior of martensitic stainless steel at high temperature is affect by evolved hydrogen atom. It is concluded that hydrogen plays a key role in the crack propagation.