The electron beam welding of super duplex stainless steels is associated with challenges due to the concentrated heat input and the nitrogen loss that result in a predominantly ferritic structure after the solidification. This study presents an approach to overcome this issue by feeding nickel-based filler wire into the melt pool in welding of 2507 super duplex stainless steel. Results showed that the high-frequency beam oscillation combined with a multi-beam technique led a good mixing between the base metal and the filler wire, even at a large depth-to-width ratio. Additionally, the weld geometry was characterized by near-parallel fusion lines and a narrow heat-affected zone. The nickel addition resulted in a balanced microstructure in the weld metal with ferrite fractions of 35–55 %, despite a significant nitrogen loss, consequently leading to impact energy values of 215 ± 15 J and hardness values of 285 ± 15 HV. The findings of this investigation allow fabricators to effectively design electron beam welding processes for producing thick-walled super duplex stainless steel components.

The duplex stainless steels have many favorable properties attributed to their two-phase microstructure consisting of almost equal fractions of ferrite and austenite. Therefore, they are widely used in the offshore, petroleum, and chemical industries as a base material for pressure vessels and pipelines. Such components often possess large thicknesses, which can be effectively welded with electron beam. This process is characterized by rapid cooling combined with a relatively great loss of nitrogen, resulting in insufficient austenite formation. To compensate this phenomenon, the addition of nickel, in the form of wire, was performed in this study. This promoted the formation of austenite at the same cooling rate, so that approximately an equal amount of ferrite and austenite was achieved. Beam oscillation was applied to maintain good dilution even at large depth/width ratios. Furthermore, the multi-beam technique was implemented to reduce the spatter formation and provide a higher process stability. This allows the spatial, but not temporal, separation of the melting-off of the wire and the main welding process. The joints produced in this way exhibit a good weld dilution and consequently an austenite distribution with a low inhomogeneity. Additionally, a narrow heat-affected zone was produced.

In recent decades, beam welding processes have been set up as a key technology for joining applications in automotive engineering and particularly in gearbox manufacturing. Due to their high beam quality, energy efficiency, reliability as well as flexible beam guidance, modern solid-state lasers offer numerous advantages, but also pose increased requirements on the production and positional accuracy of the components for the joining process. In particular, small-focus diameters present a challenge for components with process-induced tolerances, i.e., disc carriers in automatic transitions. Furthermore, welding processes utilizing solid-state lasers show an increased spatter formation during welding at high welding speeds. Accordingly, the primary objective of the presented work consists in extending the current areas of application for solid-state laser beam welding in gearbox manufacturing through an improved process reliability regarding tolerance compensation and spatter formation. Therefore, this experimental study aimed to describe the effects of a dynamic beam oscillation in combination with a reduced ambient pressure in the process environment on both gap bridging ability and spatter formation during the laser beam welding of case hardening steel. For basic process evaluations, laser beam welding at reduced ambient pressure and laser beam welding with dynamic beam oscillation were initially studied separately. Following a basic process evaluation, samples for 2 mm full-penetration-welds with varying gap sizes were analyzed in terms of weld seam geometry and weld spatter formation.

Directed energy deposition-arc (DED-arc) of duplex stainless steels faces challenges in achieving a balanced ferrite/austenite ratio in the as-deposited condition. Consequently, solution annealing is often necessary to optimize the microstructure and attain good mechanical and corrosion properties. This study explores an approach to improve the phase balance using AM 2205 wire and Ar + 2% N₂ as shielding gas. Thin-walled structures comprising 10 layers were fabricated using a waveform-controlled gas metal arc welding (GMAW) process at two different travel speeds and arc power levels. Additionally, reference samples were produced with Ar + 2.5% CO₂ to quantify the influence of shielding gas composition on austenite formation. Microstructural investigations revealed that samples produced with nitrogen-containing shielding gas had an average austenite fraction ranging from 39 to 46 vol.%, depending on the travel speed and arc power combination. This represents an average increase of 3–9 vol.% compared to traditional shielding gas.

Additive manufacturing (AM), particularly laser-based powder bed fusion (PBF-LB), enables the production of high-strength, lightweight components made of aluminum alloys such as AlSi10Mg. However, joining these parts via welding remains a significant challenge due to weld seam porosity caused by hydrogen entrapment. This study investigated the influence of the PBF-LB process parameters, tungsten inert gas (TIG) welding settings, filler material, and post-weld T6 heat treatment on the tensile strength and porosity of welded AlSi10Mg components. Using two different layer heights (30 µm and 60 µm), plate thicknesses (3 mm and 5 mm), and varying welding conditions, a series of 10 TIG-welded sample groups were fabricated and analyzed. Microstructural, hardness, porosity, and tensile tests revealed that porosity was high across all samples (11–19%). A subsequent T6 heat treatment improved the tensile strength. Higher layer heights and thinner plates led to a higher tensile strength of the weld seam, while the addition of a filler material showed limited benefits. No other influencing factors or interactions could be found. The results emphasize the need to optimize hydrogen control in the processes, melt pool dynamics, and weld seam geometry to receive reliable joints in lightweight manufacturing of PBF-LB AlSi10Mg parts.

This study provides an insight into the microstructural and mechanical properties of an electron beam welded 2507 super duplex stainless steel joint. To compensate the detrimental effect of the nitrogen loss and the cooling conditions on the austenite formation, nickel-based filler wire was fed to the weld pool to increase the amount of austenite stabilizers. A high-frequency beam oscillation combined with a multi-beam technique was applied to realize a good dilution between the base metal and the filler wire even at a large depth-to-width ratio. As a result, a good austenite-ferrite-ratio was achieved in the weld metal, leading to an impact energy of 200–230 J. The heat-affected zone exhibited a balanced microstructure and a narrow width due to the high nitrogen content of the base metal.