Laser Welding Capability from Prima Power Laserdyne
“Innovative laser processing solutions and machines”
While the origin of the LASERDYNE® product line can be traced to laser welding applications in the mid-1970’s, most people associate LASERDYNE with laser cutting and drilling for aerospace applications. Over the more than 37 years of what is now Prima Power Laserdyne, laser welding systems have been supplied for aerospace (engine and airframe), electronics, fluid couplings, and medical device applications using CO2, Nd:YAG, and fiber laser sources.
Fiber lasers enable new applications
The availability of the high power CW and QCW fiber lasers with their kilowatt-level average power, 1 µm wavelength, and high brightness (beam quality) provides a laser source with new capability and flexibility. Compared to CO2 lasers for welding, fiber lasers use fiber optic beam delivery instead of turning mirrors; have greater absorption by metals, especially those that are good conductors of electricity such as aluminum and copper; and absorbed less by the plasma plume that frequently forms above the weld pool.
Higher brightness means that the laser beam is focused to smaller sizes, which means higher power density and lower heat input. These factors contribute to deeper penetration and faster welding speed than available from previous laser sources of equivalent average power. They also lead to more stable welding processes in a wider range of metals and alloys.
Laser welding developments
Prima Power Laserdyne has made significant investment in developing process and system capability for welding 2D and 3D components with high power CW and QCW fiber lasers. Metals and alloys for which capability has been demonstrated include A36 structural steel; 300 and 400 series stainless steels; titanium alloys including Ti-6Al-4V and Ti-6Al-2Sn-4Zr-6Mo; high temperature nickel and cobalt based alloys including Inconel 625, Inconel 718, Haynes 230, and Hastelloy X; and a range of aluminum, copper, and nickel alloys.
The most comprehensive laser welding investigations have involved aerospace alloys with both CW and QCW fiber lasers. The major challenge of laser welding aerospace alloys is the stringent joint requirements measured by:
- No cracking
- Negligible porosity
- Weld geometry characterized by convex (reinforced) surfaces
- Good mechanical properties at high temperatures.
Welding trials using a range of laser and process parameters and shield gases have been performed with high power fiber lasers. Welds were characterized using metallography (cross-sections), X-ray radiography, and microhardness testing.
Through these trials, we have identified laser (spot size, focus position, laser power, etc.) and processing (shield gas type, gas flow rates, method of gas delivery, welding speed, etc.) parameters that meet the required weld geometry and microstructure.
Adding filler wire further improves quality
We have also demonstrated capability for welding with filler wire. Certain alloys and dissimilar material combinations require addition of filler material to control the structure of the weld metal and avoid cracking to ensure the required mechanical properties. In other cases, filler metal is key to controlling weld geometry, such as to create a slight convexity (reinforcement) of the weld fusion zone. Yet in other applications, filler material compensates for poor fit up and mismatch.
Laser welding with the filler wire is a multi-parameter process with a number of laser and filler wire parameters that contribute to weld quality. All of the important parameters for adding filler material have been developed and optimized to produce good quality welds.
Patent pending SmartShield™
Laser welding development by Prima Power Laserdyne has led to new features for LASERDYNE systems. One development is the SmartShield™ nozzle assembly with cross jet. SmartShield provides shielding of the weld and protects the beam delivery optics while maintaining the compact profile of the LASERDYNE third generation BeamDirector®, called BD3Y.
The cross jet of the SmartShield nozzle provides a high velocity gas barrier that prevents metal sparks from the weld zone from contaminating the protective lens cover slide. What differentiates the SmartShield nozzle from other cross jet nozzles is that the compressed air flowing through the cross jet does not contaminate or interfere with the welding shield gas. This means that the cross jet can use regular clean, compressed shop air.
The SmartShield nozzle can be used with the entire range of shield gas delivery devices including the welding shoe and coaxial gas nozzle tip. The shielding gas shoe provides a controlled atmosphere for the weld zone while it is molten and while it is cooling to a temperature at which it is no longer affected by the ambient atmosphere. This is particularly important for welding materials, such as titanium alloys, that have a strong affinity for oxygen and nitrogen in the ambient atmosphere.
Another important benefit of the design of the focusing lens/shield gas assemblies for laser welding is that they can quickly be changed between applications.
There is also better control
New capability for laser control, most notably SmartRamp™ and laser pulse shaping with sub-millisecond resolution, is also part of the latest LASERDYNE S94P control. Higher speed, higher resolution control leads to more consistent, higher quality welds.
New control also increases the flexibility of LASERDYNE systems in terms of materials to which they can be applied. By controlling the temperature profile during welding and during cooling of the weld fusion and heat affected zones, pulse shaping controls the weld profile and structure.
The shape of the laser pulse can be tailored to control heating and cooling. For example, a pulse having a high-amplitude, leading edge is often used for welding materials that are reflective to the laser beam. For these materials, absorption increases dramatically with heating of the surface. On the other hand, pulses in which the power decreases throughout the pulse have been shown to control cooling of alloys that harden upon cooling.
For more information
For details on the laser welding developments, see the various articles on laser welding on this website.
You can also request a copy of Laser Welding 101 by writing to lds.sales@primapower.com.
