Investigations into the welding of superalloys with a cw. Nd:YAG laser and dual-focusing optics

Abstract

Continuous wave Nd:YAG-lasers operating at power levels of about 3 - 4 kW are exceptionally well suited for welding thin-walled (< 5 mm) shell constructions. The goal of the present work was to investigate the possibility to weld sheet metal parts, where extremely high demands are placed on weld geometry and quality. Examples include turbine components, pressure transducers, endless bands for process industries and others applications in the aircraft and aerospace industry. Such parts are typically manufactured from stainless steel sheets and sheets of superalloys and are welded in an inert gas (Ar) atmosphere.Investigations prior to the present have shown a tendency for porosity formation in the weld. To achieve improved weld geometry and to reduce the probability of porosity formation, a new, dual-focusing optic was designed and successfully tested.Apart from stainless steels, two superalloys used within the aircraft industry, HAYNES 25 and INCONEL 718, were included in the investigation. The particular laser used was able to deliver 3 kW to the target via a 0.6 mm optical fibre. Comparison of welds produced by single and dual focusing optics was made. X-ray and metallographic investigations showed that the quality and geometry of the welds produced using the dual-focusing optics were superior to those produced with the single-focusing optics.Continuous wave Nd:YAG-lasers operating at power levels of about 3 - 4 kW are exceptionally well suited for welding thin-walled (< 5 mm) shell constructions. The goal of the present work was to investigate the possibility to weld sheet metal parts, where extremely high demands are placed on weld geometry and quality. Examples include turbine components, pressure transducers, endless bands for process industries and others applications in the aircraft and aerospace industry. Such parts are typically manufactured from stainless steel sheets and sheets of superalloys and are welded in an inert gas (Ar) atmosphere.Investigations prior to the present have shown a tendency for porosity formation in the weld. To achieve improved weld geometry and to reduce the probability of porosity formation, a new, dual-focusing optic was designed and successfully tested.Apart from stainless steels, two superalloys used within the aircraft industry, HAYNES 25 and INCONEL 718, were included in the investigation. The particular...