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Purpose: The purpose of this paper is to investigate the effect Ti on stress corrosion cracking (SCC) and flow accelerated stress corrosion cracking (FA-SCC) behavior and mechanisms of Monel K500 alloy. Design/methodology/approach: Monel K500 alloy with different Ti contents was designed. A metallurgical microscope (XJP-3C) and scanning electron microscopy (EV0 MA15 Zeiss) with an energy dispersive spectroscopy were used to analyze the microstructure of the Monel K500 alloy. In situ electrochemical tests were carried out in static and flowing seawater to study FA-SCC behavior. Findings: The number of TiCN particles in the alloy increased as the increase of Ti content. The static corrosion and SCC of Monel K500 alloy are reduced as the content of Ti increases. Generally, the SCC of alloys was caused by the synergistic effect of the anodic dissolution at exposed metal matrix and the pit corrosion of metal matrix adjacent to TiCN particles, which was further accelerated by flowing. Originality/value: The corrosion behavior and mechanism of Monel K500 alloy with different Ti contents in a complex flowing seawater environment are still unclear, which remain systematic study to insure the safe service of the alloy. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to investigate the crevice corrosion behavior and mechanism of laser additive manufacturing (LAM) nickel-based alloy under wedge-shaped crevice. Design/methodology/approach: First, the opening size of the wedge-shaped crevice was designed to 0.1, 0.3 and 0.5 mm by controlling the thickness of silicon rubber and the double-side adhesive tape. Then, one side of the glass sheet was stuck on the silicon strip and keep the electrodes of Rows 1 and 2 outside the crevice as a reference, and the opposite side was stuck to the wire beam electrode by silica gel. Findings: The current density with a maximum value of 5.7 × 10−6 A/cm2 was observed at the crevice opening of 0.5 mm, while the lowest value of 9.2 × 10−7 A/cm2 was found at the crevice opening of 0.1 mm. In addition, the corrosion resistance at the inside of the crevice is higher than that at the outside and the middle of the crevice. It means that the internal width of the wedge-shaped crevice tends toward 0, which hinders the migration of ions in the corrosive medium. The generation of corrosive products further reduce the crevice size to cause the inhibition of corrosion at the inside of the crevice as well. Originality/value: The multilayer and multipath LAM component is prepared to show the complex microstructure, which made the corrosion behavior and mechanism at wedge-shaped crevice nondeterminacy. [ABSTRACT FROM AUTHOR]

Monel K500 alloy is widely used in sea engineering and suffers the failure risk of flowing seawater under load. Therefore, the stress corrosion cracking (SCC) and flow accelerated stress corrosion cracking (FA-SCC) behavior and mechanism of aged Monel K500 alloy were investigated. Results showed that TiCN particles were observed in alloys, and the number and size of γ′ phase in Monel K500 alloy gradually increased as the aging temperature increased, while γ′ phase was not found in solution treated alloy. The yield strength of Monel K500 alloy after heat treatment and SCC experimentation was, from high to low, in the order of the ones aged at 630 °C, 700 °C, 560 °C, and solution treated. The corrosion resistance of Monel K500 alloy from high to low during SCC and FA-SCC experiments is in the order of alloys aged at 560 °C, 700 °C, 630 °C, and solution treated. Pit corrosion was found at the matrix adjacent to TiCN particles, and cracks were mainly observed at grain boundaries (GBs) after SCC and FA-SCC experiments and after tensile testing. Generally, the SCC of alloys was caused by the synergistic effect of the anodic dissolution at exposed metal matrix and the pit corrosion of metal matrix adjacent to TiCN particles, which was further accelerated by flowing. [ABSTRACT FROM AUTHOR]

Ensemble learning (EL) models were developed to predict the pitting potential (E p) of alloys. By carefully selecting features and optimizing parameters, the predictive accuracy of the models was improved and experimentally validated. Interpretability methods, SHapley Additive exPlanations (SHAP), Partial Dependence Plot (PDP), and Accumulated Local Effect (ALE), explained the model's prediction logic effectively and portrayed the effects of alloying elements, thermodynamic parameters, and environmental factors on E p in detail. Furthermore, performance differences between interpretability methods, errors in model prediction, and failure cases of interpretability methods were discussed, which provided insights for model optimization and appropriate Interpretability methods selection. [Display omitted] • The performance of EL models (RF, AdaBoost, XGBoost, Stacking) and DNN were compared. • Quantitatively analyzed the effect of features on E p using interpretability methods. • For the first time, the differences among interpretability methods were discussed. • Failure situations for model prediction and interpretability methods were analyzed. • Predictive model was experimentally validated and explained alloy corrosion. [ABSTRACT FROM AUTHOR]

The use of cold metal transfer process (CMT) is an excellent alternative to depositing nickel-based alloys on oil and gas pipelines due to the relatively small dilution. However, sulfide stress corrosion cracking (SSCC) of dissimilar weld joints has proven to be an issue. Therefore, this study investigates the microstructure and SSCC behavior of an Inconel 625/X80 weld overlay fabricated CMT process focusing on the tempering effect. Four-point bending tests show a high SSCC susceptibility of the non-overlap zone due to the formation of coarse structure in the heat affected zone and narrow martensite layer along the fusion boundary. However, microstructural characterization indicates a tempering effect in the overlap zone, producing homogenized microstructure and less residual strain in the heat affected zone. Therefore, the SSCC resistance is greatly improved, especially for the fusion boundary, because reversed austenite in the martensite layer could decrease the accumulation of hydrogen at lath boundaries. [Display omitted] • Martensite layer induces sulfide stress corrosion cracking of the fusion boundary (FB). • Tempering effect produces homogenized microstructure and less residual strain. • Reversed austenite exists in the martensite layer along the FB in the overlap zone. • Sulfide stress corrosion cracking of FB is improved by the reversed austenite. [ABSTRACT FROM AUTHOR]