Papers by Keyword: Stress Corrosion Cracking

Abstract: This study aimed to demonstrate the susceptibility of 5% Ni steel to stress corrosion cracking, SCC, in anhydrous liquid ammonia. SCC tests using four-point bend specimens cut from welds in SPV315, HT780 and 5% Ni steel were carried out in anhydrous liquid ammonia with 5wt% NH₄CO₂NH₂ and 0.1MPa O₂ at +2.0V, which is an accelerated SCC test condition. No SCC was observed in SPV315, whose strength is within the allowable strength of IGC code 17.12, but SCC was observed in the HAZ of HT780, whose strength is higher than the upper limit of IGC code 17.12. Furthermore, SCC was recognized in the HAZ and base metal of 5% Ni steel, whose nickel content is higher than the upper limit of IGC code 17.12, and this suggests that 5% Ni steel is susceptible to SCC in anhydrous liquid ammonia.

Abstract: Final turning, which is a finishing process for obtaining components with specific precise parameters, affects the integrity of the surface and its properties, whether hardness or surface residual stresses. The synergistic effect of these factors affects the susceptibility of the material, to stress corrosion cracking. In this work, 2 types of austenitic stainless steel, namely AISI 304 and AISI 321, were turned. Tool with positive cutting geometry was used for turning. The cutting parameters that varied were the cutting speed (100 and 250 m.min⁻¹) and the tool feed (0.12, 0.2 and 0.3 mm·rev⁻¹). The depth of cut was the same for all turnings (0.8 mm). Subsequently, the prepared samples were exposed in MgCl₂ solution based on the ASTM G36 for 96 hours. After this time, the samples were analysed using SEM, where the density of surface cracks was monitored. When comparing the crack density, an increase in density was visible for AISI 304 compared to AISI 321. It was shown that with increasing cutting speed, the density of cracks increased significantly, as well as with increasing tool feed. On the cross-sections the depth and length of the cracks were analysed. Crack depth and length increased with increasing feed too.

Abstract: This study investigates the stress corrosion cracking (SCC) behavior of Aluminum in chloride solutions, focusing on varying bending angles (0°, 90°, and 180°), temperatures (25°C, 35°C, and 45°C), and NaCl concentrations (1%, 2%, and 3.5%). Bending tests using a universal testing machine and corrosion tests employing the open circuit potential (OCP) method and anodic polarization Tafel method were conducted. Results revealed that the highest balanced potential (-0.33684 V) occurred at a 0° bend angle in distilled water, while the lowest (-1.02513 V) was at a 180° bend angle in 3.5 wt% NaCl solution. The lowest corrosion rate (0.002403953 mmpy) was observed at a 0° bend angle in distilled water at 25°C, and the highest (2.18789227 mmpy) at a 180° bend angle in 3.5 wt% NaCl solution at 45°C. Surface characterization indicated significant pitting corrosion in NaCl solutions, particularly at a 180° bend angle, while no pitting was seen in distilled water. These findings highlight the substantial impact of bending angle and chloride concentration on the SCC behavior of Aluminum, providing valuable insights for its application in corrosive environments.

Abstract: In this investigation, the resistance of brass material to stress corrosion cracking (SCC) in a chloride solution was assessed through adjustments in temperature (25°C, 35°C, and 45°C) and bending angles of the brass material (1.0 wt%, 2.0 wt%, and 3.5 wt%). The chosen solution closely resembles saltwater, making it suitable for testing, especially considering the widespread use of brass materials in various industrial sectors, particularly shipping. Stress corrosion cracking tends to impact brass materials under heavy loading. The primary objective of this study is to characterize the corrosion rate of brass materials. The method involved a bending test with angle variations of 180°, 90°, and 0°. Corrosion assessment utilized the Open Circuit Potential method, Anodic Polarization Tafel, and a digital microscope for the material's microstructure properties. According to the findings, brass material exhibits the lowest corrosion rate (10 x 10^-6 mmpy) at a temperature of 25°C distilled water and an angle variation of 0°. Conversely, the corrosion rate increases with variations in bending angle, temperature, and the concentration of NaCl solution, as evidenced by the corrosion rate of 28.035 x 10^-5 mmpy with an angle variation of 180°, to a corrosive solution of NaCl 3.5 wt% at a temperature of 45°C.

Abstract: Despite its remarkable structural strength, austenitic stainless steels such as SS304 are susceptible to stress corrosion cracking (SCC) under thermal insulation due to the synergism of cyclic loading and chloride-containing environments. This study aims to detect SCC for insulated SS304 samples using the acoustic emission technique (AET) as monitoring tool to characterize the various stages of SCC damage mechanism. As-received (AR) and sensitized (SEN) SS304 samples were prepared as per ASTM G30 and experimented with soluble chloride drip test under calcium silicate thermal insulation following ASTM C692. Both AR and SEN samples revealed SCC behavior correlated with measured acoustic signals. AR samples exhibited a single crack with low energetic signals, whereas SEN showed multiple cracks with higher energetic signal events. The difference can be attributed to microstructure change by heat sensitization and the enhancement of the corrosion environment under calcium silicate insulation when wetted by salt solution. The acoustic emission (AE) parameters were characterized and correlated with different stages of SCC phenomena, showing that AET is useful for predicting SCC to avoid catastrophic failures in industries.

Abstract: As part of the project “Thermostat for universal use in (electro) mobility”, an analysis of three currently used thermostats failed during operation was performed. In all three cases, cracks occurred in the brass outer casings. The cracks were open and fractographical observation was performed. The microstructure of the material was evaluated using both the light and scanning electron microscopy. The local composition of the material was determined by EDS microanalysis. Furthermore, hardness profiles were measured. The cracks were predominantly intergranular with a smaller portion of transgranular cleavage. The microstructure was formed by a mixture of α- and β-phase grains and lead particles. In addition to the stress caused by the overpressure of the molten wax, a higher level of residual stresses caused by deformations can be expected. The failure was caused by the mechanism of stress-corrosion cracking. Metal induced embrittlement or/and corrosion fatigue could interact too.

Abstract: The present work deals with the causes of the damage to the distribution wheel of the main circulation pump of the nuclear power plant. During the solution of the problem, a significant influence of the final machining on the formation of cracks was found. Coarse surface machining can cause strain-induced martensite on the distribution wheel surface. Small pitting, which was observed on the surface of the distribution wheel, can be caused by the presence of martensite with less corrosion resistance. Thermal stress and residual stress after coarse final surface machining caused the growth of the cracks which initiated from the pitting.

Abstract: The mains reasons for internal corrosion failure and cracking of the tee in shale gas transportation platform have been proposed based on macroscopic analysis, physical and chemical property test, metallographic examination, Scanning Electron Microscope analysis, X-ray spectroscopy analysis and service condition analysis. The results show that corrosion occurring in the inner wall of tee was caused by the combined impacts of CO₂ corrosion, sulfate-reducing bacteria (SRB) corrosion and erosion corrosion. The crack in the weld of the inner wall was mainly due to the Sulfate-reducing Bacteria Induced cracking.

Abstract: The influence weights of various sensitive factors, such as steel grade, applied potential, temperature and soil environment, on stress corrosion cracking behavior of high-grade pipeline steel were studied by means of orthogonal test at mixed level and slow strain rate test. The stress corrosion behavior of X80 pipeline steel in near neutral and high pH simulated soil solution under overprotection potential was observed by SEM. The results showed that the applied potential has the greatest weight on stress corrosion index of ISSRT, followed by temperature, steel grade and soil environment. X80 pipeline steel exhibits high stress corrosion sensitivity in near-neutral and high pH simulated soil solutions at applied potential of -1500mV, and its SCC mechanism is hydrogen embrittlement (HE). This study can provide guidance for practical engineering application of pipeline steel.

Abstract: The stress corrosion cracking (SCC) sensitivity of aged Z3CN20.09M stainless steel (SS) was investigated by scanning electrochemical microscopy (SECM), nanoindenter and slow strain rate tensiometer (SSRT). The results indicated that the hardness and modulus of the samples increased with increasing aging time at 475 °C, which increased about 80% and 15% respectively after aging for 1000h. After immersed in NaCl+HCl solution (pH=2) for 7 h, the pitting corrosion point appeared of specimen aged for 1000h. While it was not found even for 24 h of as-received (AR) and aged for 500 h specimens at the same condition. The SCC sensitivity was increased about one time of the specimen aged for 1000 h tested in 300 °C high temperature water. The combined effect associated the embrittlement of mechanical properties and the decrease of corrosion resistance is regarded as the main reason for the increasing of SCC sensitivity.