Effect of post-weld heat treatment on fusion boundary microstructure in dissimilar metal welds for subsea service
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Carolin Fink
Abstract
Microstructural features at the fusion boundary in dissimilar metal welds significantly influence the susceptibility to local hydrogen embrittlement under subsea service conditions. Two subsea dissimilar metal welds using nickel-based filler metal on low alloy steel substrate were studied in this work in order to investigate the nature and microstructural evolution of the dissimilar interface during post-weld heat treatment (PWHT), and to determine resistance to hydrogen embrittlement. The delayed hydrogen cracking test (DHCT) was utilized to determine hydrogen-assisted cracking (HAC) susceptibility. Thermokinetic modeling was conducted to study phase formation and carbon diffusion across the dissimilar interface. Diffusion calculations incorporated initial compositional gradients after welding and the nonmoving phase boundary during PWHT. Resistance to HAC was in good agreement with previously obtained DHCT results for the tested dissimilar metal welds. Tempered martensite in the heat-affected zone of the steel substrate was observed as a function of PWHT temperature. Fresh martensite with high local hardness formed during cooling in highly diluted weld metal regions. The cell model incorporated in DICTRA effectively predicted differences in carbon concentration profiles across the dissimilar interface and type of carbide precipitation as a function of PWHT procedure and steel substrate.
Kurzfassung
Die Gefügeausbildung entlang der Schmelzlinie von Mischschweiβverbindungen ist von groβer Bedeutung für deren Anfälligkeit gegenüber Wasserstoffversprödung bei Betrieb im Offshore- und Unterwasserbereich. Im Rahmen dieser Studie wurden zwei typische Mischverbindungen aus Ni-Basis-Schweiβgut auf niedriglegiertem Stahl bezüglich Veränderungen im Gefüge der Bindezone durch Wärmebehandlung und auf Beständigkeit gegenüber Wasserstoffversprödung untersucht. Als Prüfverfahren zur Beurteilung der wasserstoffunterstützten Kaltrissbeständigkeit der Mischverbindungen wurde der Delayed Hydrogen Cracking Test (DHCT) herangezogen. Proben mit horizontal zur Belastungsrichtung verlaufender Schmelzlinie wurden elektrolytisch mit Wasserstoff beladen und gleichzeitig einer konstanten Zugbeanspruchung ausgesetzt. Die Standzeit bis zum Versagen der Proben wurde als quantitatives Testkriterium herangezogen. Die Diffusion von Kohlenstoff und die Bildung von Carbiden im Bereich der Schmelzlinie während der Wärmebehandlung wurde mittels thermodynamischer Simulationen in ThermoCalc und DICTRA untersucht. Die Kaltrissprüfergebnisse zeigen eine gute Übereinstimmung mit früheren DHCT-Tests an den untersuchten Mischverbindungen. In der Wärmeeinflusszone der Stahlgrundwerkstoffe wird die Martensitphase in Abhängigkeit von der Höhe der Wärmebehandlungstemperatur unterschiedlich stark angelassen. In Bereichen entlang der Schmelzlinie mit hoher Aufmischung mit dem Ni-Basisschweiβgut bildet sich bei der Abkühlung frischer Martensit mit hoher Härte. Das Simulationsmodel in DICTRA beschreibt Unterschiede im Kohlenstoffprofil und der Ausscheidung von Carbiden in der Bindezone der Mischverbindungen in Abhängigkeit der Wärmebehandlung und des niedriglegierten Stahlgrundwerkstoffes.
References
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© 2017, Carl Hanser Verlag, München
Artikel in diesem Heft
- Inhalt/Contents
- Contents
- Fachbeiträge/Technical Contributions
- The principles of measurement and testing to characterize material properties
- Electrochemical behavior of alloy AgCu50 during oxidation in the presence of chlorides and benzotriazole
- Mechanical property effects of symmetrical hour glass shapes formed during double-sided TIG keyhole arc welding of AISI1040 joints
- Residual stress state in pipe cut ring specimens for fracture toughness testing
- Effect of overlap length and scarf angle on the mechanical properties of different adhesive joints subjected to tensile loads
- Effect of post-weld heat treatment on fusion boundary microstructure in dissimilar metal welds for subsea service
- Effects of abaca fiber reinforcement on the dynamic mechanical behavior of vinyl ester composites
- Experimental and theoretical study of the rubbing process of epoxy composites against steel
- Structural self-organization of titanium alloys under impulse force action
- Effect of SiC particle size on the mechanical properties of closed aluminum foams
- Comparison of different bushing applications in composite structures of the aerospace industry
- Performance monitoring of superlarge-diameter rock-socketed piles by optic fiber sensors
- Free vibration of a Timoshenko beam carrying three dimensional tip mass: Analytical solution and experimental modal testing
- Electrochemical properties of LaNi4.2Co0.4Zn0.1Al0.3 and LaNi4.3Co0.4Zn0.1Al0.2 alloys as anode materials for Ni-MH batteries
- Production of hard hydrophilic Ni-B coatings on hydrophobic Ni-Ti and Ti-6Al-4V alloys by electroless deposition
Artikel in diesem Heft
- Inhalt/Contents
- Contents
- Fachbeiträge/Technical Contributions
- The principles of measurement and testing to characterize material properties
- Electrochemical behavior of alloy AgCu50 during oxidation in the presence of chlorides and benzotriazole
- Mechanical property effects of symmetrical hour glass shapes formed during double-sided TIG keyhole arc welding of AISI1040 joints
- Residual stress state in pipe cut ring specimens for fracture toughness testing
- Effect of overlap length and scarf angle on the mechanical properties of different adhesive joints subjected to tensile loads
- Effect of post-weld heat treatment on fusion boundary microstructure in dissimilar metal welds for subsea service
- Effects of abaca fiber reinforcement on the dynamic mechanical behavior of vinyl ester composites
- Experimental and theoretical study of the rubbing process of epoxy composites against steel
- Structural self-organization of titanium alloys under impulse force action
- Effect of SiC particle size on the mechanical properties of closed aluminum foams
- Comparison of different bushing applications in composite structures of the aerospace industry
- Performance monitoring of superlarge-diameter rock-socketed piles by optic fiber sensors
- Free vibration of a Timoshenko beam carrying three dimensional tip mass: Analytical solution and experimental modal testing
- Electrochemical properties of LaNi4.2Co0.4Zn0.1Al0.3 and LaNi4.3Co0.4Zn0.1Al0.2 alloys as anode materials for Ni-MH batteries
- Production of hard hydrophilic Ni-B coatings on hydrophobic Ni-Ti and Ti-6Al-4V alloys by electroless deposition