#Breakthrough in Metal Additive Manufacturing

A groundbreaking study from Cranfield University has revealed that controlling interpass temperature (IPT) during Cold Wire Gas Metal Arc (CW-GMA) additive manufacturing can significantly enhance production efficiency while maintaining the superior mechanical performance of super duplex stainless steel (SDSS). The research team demonstrated that increasing IPT from 75°C to 350°C reduced waiting times between deposition passes from over 20 minutes to just 3 minutes, potentially revolutionizing the industrial application of this technology for critical components in demanding environments.

#The Delicate Balance of Super Duplex Steel

Super duplex stainless steels represent a premium class of materials prized for their exceptional combination of strength and corrosion resistance. These properties stem from their carefully balanced microstructure, which ideally consists of approximately equal proportions of ferrite and austenite phases. Maintaining this delicate balance during additive manufacturing processes has historically been challenging, as the repeated heating and cooling cycles can disrupt the optimal phase distribution. The CW-GMA process offers enhanced control over heat input, a crucial factor for preserving the microstructural integrity that gives SDSS its valuable properties.

#Thermal Management Without Compromise

The Cranfield study specifically evaluated three different interpass temperature settings, 75°C, 200°C, and 350°C, during the fabrication of UNS S32906 SDSS components. Despite the significant differences in thermal exposure, detailed microstructural analysis revealed that the critical ferrite-austenite phase balance remained remarkably consistent across all temperature conditions. While higher temperatures did promote the formation of fine secondary austenite near fusion boundaries, this had minimal impact on the overall phase distribution that determines the material's performance characteristics.

#Impressive Mechanical Performance

Perhaps most striking were the mechanical testing results, which showed ultimate tensile strengths of approximately 810 MPa across all IPT conditions. These values not only remained consistent regardless of processing temperature but actually exceeded the typical strength values reported for conventionally manufactured SDSS components. Hardness measurements also showed stability across the different thermal conditions, averaging around 300 Hv. These findings demonstrate that the CW-GMA process can produce SDSS components with superior mechanical properties even when optimized for faster production speeds.

#Production Efficiency Gains

The most significant practical implication of the research is the dramatic reduction in manufacturing time achieved at higher interpass temperatures. By increasing IPT from 75°C to 350°C, the researchers reduced the cooling wait time between successive deposition passes from over 20 minutes to just 3 minutes, a nearly 85% reduction in idle time. This improvement in process efficiency could transform the economic viability of additive manufacturing for larger SDSS components, particularly for industries like offshore energy, petrochemical processing, and maritime applications where these materials are most valuable.

#Challenges and Ongoing Research

Despite the promising results, the researchers identified porosity as a remaining challenge, particularly at higher interpass temperatures. The presence of internal voids influenced the ductility of the fabricated components, suggesting that further optimization is needed. Current research efforts are focusing on improved gas shielding techniques and exploring in-process deformation methods to minimize porosity formation. These refinements could further enhance the mechanical performance of additively manufactured SDSS components, particularly in applications where fatigue resistance is critical.

#Industry-Wide Focus on Thermal Control

The Cranfield findings align with a broader industry trend toward sophisticated thermal management in metal additive manufacturing. Companies like WAAM3D are introducing systems with advanced thermal monitoring capabilities, while simulation tools such as FLOW-3D AM are helping engineers model and optimize temperature-dependent phenomena during fabrication. Complementary research at MIT has developed post-processing techniques that modify metal microstructures to improve thermal resistance. Collectively, these developments underscore the critical importance of temperature control in ensuring quality, reliability, and commercial viability of metal additive manufacturing technologies.

#Key Takeaways:

• Increasing interpass temperature from 75°C to 350°C in CW-GMA additive manufacturing reduces production time by 85% without compromising the mechanical strength of super duplex stainless steel

• Additively manufactured SDSS components achieved ultimate tensile strengths of approximately 810 MPa, exceeding values typically reported for conventionally processed materials

• Thermal management continues to emerge as a critical focus area across the metal additive manufacturing industry, with new tools and techniques being developed to optimize temperature-dependent properties