The Different Laser Beam vs. Electron Beam Welding

Proponents of laser beam welding (LBW) and electron beam welding (EBW)  each pronounce the singular praises of their favored technology, but often the best solution for a customer is to use both technologies together. Both processes are well suited to joining components with complex geometries, and capable of meeting the most stringent demands for metallurgical characteristics of the final assembly.

 

Laser beam welding (LBW) 

 

Laser welding energy sources utilize either a continuous wave (CW) or pulsed output of photons. With CW systems, the laser beam is always on during the welding process. Pulsed systems are modulated to output a series of pulses with an off time between those pulses. With both methods, the laser beam is optically focused on the workpiece surface to be welded. These laser beams may be delivered directly to the part via classical hard-optics, or through a highly flexible fiber optic cable capable of delivering the laser energy to distant workstations.

 

It is the high energy density of the laser that allows the surface of the material to be brought to its liquids temperature rapidly, allowing for a short beam interaction time compared to traditional welding methods such as GTAW (TIG welding) and similar processes. Energy is thus given less time to dissipate into the interior of the workpiece. This results in a narrow heat-affected zone and less fatigue debit to the component.

 

Electron beam welding (EBW) 

 

Widely accepted across many industries, EBW permits the welding of refractory and dissimilar metals that are typically unsuited for other methods. The kinetic energy of the electrons is converted to heat energy, which in turn is the driving force for fusion. Usually no added filler material is required or used, and post-weld distortion is minimal. Ultra-high energy density enables deep penetration and high aspect ratios, while a vacuum environment ensures an atmospheric gas contamination-free weld that is critical for metals such as Electron Beam Welding titanium, niobium, refractory metals, and nickel-based super-alloys.

 

However, the main necessity for operating under vacuum is to control the electron beam precisely. Scattering occurs when electrons interact with air molecules; by lowering the ambient pressure electrons can be more tightly controlled. Modern vacuum chambers are equipped with state-of-the-art seals, vacuum sensors, and high-performance pumping systems enabling rapid evacuation. These features make it possible to focus the electron beam to diameters of 0.3 to 0.8 millimeters. By incorporating the latest in microprocessor Computer Numeric Control (CNC) and systems monitoring for superior part manipulation, parts of various size and mass can be joined without excessive melting of smaller components. The precise control of both the diameter of the electron beam and the travel speed allows materials from 0.001” to several inches thick to be fused together. These characteristics make EBW an extremely valuable technology.

 

Electron beam welding (EBW) and Laser beam welding (LBW) are two very popular methods of joining multiple metallic components. But which process is the most effective?  The answer to this question depends on the welding application. In most cases, it is very beneficial to utilize both processes at different stages, especially with more complex manufacturing processes and components. Laser processing is required either when the size of the final assembly is too large for an EB welding chamber, some component in an assembly is incompatible with vacuum processing (such as a liquid or gas), or when the weld is inaccessible to an electron beam source. Electron beam will be the primary choice when the completed assembly must be sealed with internal components under vacuum, when weld penetrations exceed 1⁄2", when the material is challenging to initiate laser coupling, or when the weld must not be exposed to atmospheric conditions until it has cooled to an acceptable temperature. Examples are aerospace welding of titanium and its alloys, and many refractory metals such as tungsten, niobium, rhenium, and tantalum.