A research team from Cranfield University has demonstrated that controlling interpass temperature (IPT) in Cold Wire Gas Metal Arc (CW-GMA) additive manufacturing can enhance process productivity without compromising the mechanical performance of super duplex stainless steel (SDSS) parts.
The study, published in the Journal of Manufacturing Processes, evaluates the effects of three IPT settings, 75 °C, 200 °C, and 350 °C, on the microstructure and mechanical properties of UNS S32906 SDSS during wire-directed energy deposition. Despite notable differences in thermal accumulation and grain coarsening, the results show minimal impact on phase balance or tensile strength.
Balancing heat and performance
Super duplex stainless steels are prized for their high strength and corrosion resistance, characteristics derived from a roughly equal mix of ferrite and austenite phases. However, maintaining this balance during additive manufacturing remains a challenge, particularly under fluctuating thermal conditions. The CW-GMA process, which incorporates a cold wire feed into a gas metal arc setup, offers greater control over heat input, a critical factor for phase stability in SDSS.
While higher IPTs led to greater thermal exposure and the formation of fine secondary austenite near fusion lines, the overall ferrite–austenite ratio remained consistent. Tensile testing revealed ultimate strengths of ~810 MPa across all IPTs, exceeding values commonly reported for conventionally processed SDSS. Hardness levels also remained stable, averaging ~300 Hv.
Implications for industrial adoption
Importantly, increasing IPT from 75 °C to 350 °C reduced interpass dwell time from over 20 minutes to just 3 minutes, significantly boosting deposition speed without degrading mechanical integrity. This finding suggests that higher IPTs could help scale CW-GMA additive manufacturing for larger structural components, such as those used in offshore, petrochemical, or energy infrastructure.
“Optimizing interpass temperature provides a pathway to more efficient manufacturing workflows while preserving the performance characteristics of SDSS,” the authors conclude.
Future directions
The researchers acknowledge that porosity remains a factor influencing ductility, particularly at higher IPTs. Ongoing work will explore gas shielding improvements and in-process deformation techniques to reduce internal voids.
CW-GMA continues to emerge as a versatile approach for metal additive manufacturing, particularly for challenging alloys like super duplex stainless steels. As industries seek more scalable solutions, fine-tuning thermal parameters like IPT could become key to balancing speed, structure, and strength.
Thermal control emerges as key focus in metal additive manufacturing
Temperature management continues to play a pivotal role in advancing metal additive manufacturing, where precise control over heat input and cooling rates is key to ensuring microstructural stability and mechanical performance. Across the industry, new tools and techniques are emerging to meet this challenge. WAAM3D recently introduced the MiniWAAM system, which integrates advanced thermal monitoring and multi-material compatibility within arc-based additive manufacturing workflows. Meanwhile, simulation software like FLOW-3D AM is helping engineers model and optimize melt pool dynamics, offering deeper insight into how temperature influences solidification and defect formation. In parallel, MIT researchers have developed a post-processing method that alters metal microstructures to significantly improve thermal resistance and durability. These developments reflect a growing industry focus on temperature as a core variable in ensuring the quality, reliability, and scalability of metal 3D printing technologies.
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Feature image shows cross-section macrographs and microstructure at different magnifications of SDSS CW-GMA walls under different interpass temperatures. Image via Poulain et al., Journal of Manufacturing Processes
