Hybrid welding opens new possibilities for thick duplex steel fabrication

As manufacturers continue to push for greater productivity without sacrificing quality, joining thick-section duplex stainless steels remains one of fabrication's most demanding challenges. Industries such as offshore energy, shipbuilding, petrochemicals, desalination, and heavy process equipment increasingly rely on duplex steels for their excellent combination of strength and corrosion resistance. Yet welding these advanced materials efficiently has long presented a difficult compromise.

Researchers at Germany's Laser Zentrum Hannover e.V. (LZH) are working to change that. Through the LaHDusch research project, they are developing an innovative laser-arc hybrid welding process designed specifically for thick duplex steel sections up to 30 mm, combining the productivity of laser processing with the proven metallurgical performance of arc welding.

Why Duplex Steels Are Challenging to Weld

Duplex stainless steels derive their exceptional performance from a carefully balanced microstructure consisting of approximately equal proportions of ferrite and austenite. This unique combination offers several important advantages over conventional stainless steels, including: High mechanical strength; Excellent resistance to chloride stress corrosion cracking; Superior pitting and crevice corrosion resistance; Good fatigue performance; and Reduced material thickness requirements in structural applications.

These characteristics have made duplex grades increasingly attractive wherever components must withstand aggressive environments while maintaining structural integrity.

However, maintaining this balanced microstructure during welding is far from straightforward.

The welding thermal cycle significantly influences the ferrite-to-austenite ratio. Excessive or poorly controlled heat input can alter phase balance, reducing corrosion resistance, toughness, and overall mechanical performance. This places considerable demands on welding process selection and parameter optimisation.

The Productivity Versus Quality Trade-Off

Current welding technologies each offer distinct advantages but also clear limitations when applied to thick duplex materials.

Traditional arc welding methods—including Gas Metal Arc Welding (GMAW)—are well established and capable of producing high-quality welds with excellent metallurgical characteristics. However, their relatively low travel speeds and multiple-pass requirements can significantly extend production times when welding thick plates.

Laser beam welding, by contrast, offers dramatically higher travel speeds and lower overall heat input, resulting in reduced distortion and improved productivity. Yet for thicker duplex sections, laser welding alone often struggles to achieve the required weld geometry, filler metal addition, and metallurgical quality necessary for demanding industrial applications.

Manufacturers are therefore frequently forced to choose between production efficiency and weld performance.

Combining Two Heat Sources into One Process

The LaHDusch project seeks to overcome this long-standing compromise by integrating two complementary heat sources into a single hybrid welding process.

Rather than relying solely on either laser or conventional arc technology, the process combines: A high-energy laser beam; A non-transferred electric arc; Pulsed wire feeding; and An additional pulsed consumable wire.

This coordinated approach allows each technology to contribute its strengths while compensating for the other's limitations.

The laser beam provides concentrated energy for deep penetration and high welding speeds. Meanwhile, the non-transferred arc supplies filler material efficiently without introducing excessive thermal load into the workpiece.

How the Hybrid Process Works

Unlike conventional arc welding, the non-transferred arc in this process burns between two continuously fed welding wires rather than directly between the electrode and the workpiece.

This configuration offers several important process advantages.

The arc melts the filler wire efficiently, enabling high deposition rates while minimising direct heat input into the base material. Reduced thermal loading helps preserve the carefully balanced duplex microstructure that is essential for corrosion resistance and mechanical strength.

An additional pulsed consumable wire further stabilises the weld pool and improves overall weld quality by optimising filler metal delivery.

The combined system enables simultaneous deep penetration from the laser and controlled filler deposition from the arc, producing welds that balance productivity with metallurgical integrity.

More Than Process Development

The LaHDusch project extends beyond laboratory-scale welding trials.

Alongside process development, the project partners are working to establish industrial-grade system technology suitable for practical manufacturing environments. This includes equipment integration, process control, and automation capabilities that could allow manufacturers to adopt the technology within existing production systems.

Project partner MERKLE Schweißanlagen-Technik GmbH is responsible for developing the innovative arc welding technology that forms a key component of the hybrid system.

The collaboration reflects an increasing trend toward interdisciplinary manufacturing solutions that combine advances in laser technology, arc welding, materials science, and intelligent process control.

Benefits for Heavy Industry

If successfully commercialised, the hybrid process could deliver significant advantages across industries that routinely fabricate thick corrosion-resistant structures.

Potential benefits include: Faster welding of thick duplex steel plates; Higher deposition rates with controlled heat input; Improved preservation of duplex microstructure; Reduced distortion; Fewer welding passes; Greater process efficiency; and Enhanced productivity without compromising weld quality.

These improvements could be particularly valuable for small and medium-sized manufacturers, many of which face increasing pressure to shorten production cycles while maintaining stringent quality standards.

Applications could extend across offshore platforms, pressure vessels, chemical processing equipment, pipelines, marine structures, renewable energy infrastructure, and other sectors where duplex stainless steels are widely used.

Supporting the Future of Advanced Welding

As manufacturers increasingly adopt high-performance materials, welding technology must evolve to keep pace. Hybrid manufacturing processes that combine multiple energy sources are emerging as an important direction for modern fabrication, offering opportunities to improve both productivity and material performance.

The LaHDusch project demonstrates how combining laser processing with advanced arc welding can address longstanding manufacturing challenges rather than forcing engineers to compromise between speed and quality.

The project, titled "Process Development for Laser Beam Hybrid Welding with Non-Transferred Arc and Melt-Stimulating Wire Feeding (LaHDusch)," is funded through Germany's Central Innovation Program for SMEs (ZIM) by the Federal Ministry for Economic Affairs and Energy. The initiative aims to accelerate innovation that can be transferred from research into practical industrial manufacturing.

As demand for stronger, more corrosion-resistant materials continue to grow across heavy industries, developments such as laser-arc hybrid welding could play an increasingly important role in enabling faster, more reliable, and more cost-effective fabrication of next-generation engineered structures.