In the sphere of metal processing, combating oxidation poses a significant challenge. The approach of LZH scientists involve conducting production in an oxygen-free environment.
The independent, non-profit research institute, the Laser Zentrum Hannover e.V. actively explores the application of this concept in laser beam brazing and additive manufacturing processes.
The Oxygen is a disruptive element in various metalworking production processes, leading to the formation of oxide layers that impede workpiece joining and hasten component and tool wear. The Collaborative Research Center (CRC) 1368, titled “Oxygen-Free Production,” employs a novel method to tackle the oxidation issue. Researchers introduce argon protective gas with a small amount of silane during production. Silane reacts with surrounding oxygen, creating an atmosphere akin to an extremely high vacuum (XHV). This atmosphere boasts an exceptionally low oxygen content, resembling conditions in a technical vacuum but at a significantly lower cost. At LZH, scientists investigate the effectiveness of this oxygen exclusion method in powder-bed-based laser beam melting and laser beam brazing.
Laser Beam Brazing Without Flux
In a specific subproject, the Joining and Cutting of Metals group has developed a groundbreaking brazing process that eliminates the need for flux. Typically, fluxes are employed to break up the oxide layer on material surfaces, facilitating the reaction between metal and filler material. In this newly devised process, LZH researchers employ a nanosecond-pulsed laser beam source to break the oxide layer. The subsequent brazing occurs under a continuous-wave (cw) laser beam in a silane atmosphere, preventing re-oxidation of the surface between process steps.
The researchers have successfully demonstrated the permanent removal of the oxide layer on aluminum alloys in an oxygen-free atmosphere, enabling wetting of the surface with a compatible solder material. In the ongoing research, the team aims to extend the process to the challenging mixed connection of aluminum and copper, exploring the associated process limits.
Additive Manufacturing in an Oxygen-Free Atmosphere
The Additive Manufacturing – Metals group investigates the processing of metal powders in an oxygen-free atmosphere using laser-based powder bed fusion of metals (PBF-LB/M). The process, developed with the titanium alloy Ti-6Al-4V, has been monitored using high-speed cameras on a specially designed PBF-LB/M system. The primary objective of this subproject is to gain a fundamental understanding of the process in an oxygen-free atmosphere and its impact on oxygen presence. Initial results indicate a more stable process with fewer splatters and improved component properties.
Further researches in the second funding period will focus on eliminating moisture from the atmosphere and powder for enhanced process and component quality.
Have a look at the video made by LZH: