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Influence of Heat Input on Phase Balance, Microstructural Evolution, and Mechanical Performance of Super Duplex Stainless Steel Welded by Gas Tungsten Arc Welding
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DOI：10.1007/s11665-026-13845-8.png)
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Abstract
En 中文
Super duplex stainless steels (SDSSs) are widely used in offshore, marine, and chemical processing industries due to their excellent combination of high strength and corrosion resistance; however, improper heat input during welding can disturb the ferrite-austenite phase balance and consequently degrade mechanical performance. In gas tungsten arc welding (GTAW) of SDSS, precise control and monitoring of heat input are essential to maintain the desired phase balance and to prevent the formation of undesirable intermetallic phases. This study investigates the influence of controlled heat input on phase balance, microstructural evolution, and mechanical properties of UNS S32750 GTAW-welded SDSS, with the objective of identifying an optimal thermal input window for reliable joint performance. The weld joints were created under three heat input conditions (low, medium, and high) with varying welding parameters including variation of welding current, voltage, and travel speed. Microstructural characterization was performed using optical microscopy and fractographic analysis, while mechanical behavior was evaluated through tensile and hardness testing. The experimental results demonstrate that the weld metal zone exhibited maximum tensile strength (648 MPa) and hardness (265 HV) under the medium heat input condition, indicating an optimal balance between ferrite-austenite phase distribution and thermal control. Fractographic analysis revealed brittle or mixed-mode fracture characteristics at medium heat input, whereas predominantly ductile fracture was observed under optimized welding parameters. The results indicate the importance of medium heat input during the provision of good weld quality and dependable mechanical properties on GTAW-welded components of the super duplex stainless steel.
Keywords:
fractographic analysis
GTAW
hardness
heat input
super duplex stainless steels
tensile strength
weld metal zone
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