flying greater distance (15,000 km). As a result, aerospace manufacturers are aggressively investigating new approaches to aircraſt design, materials and manufacturing methods. Key drivers are reducing the weight of an aircraſt in order to reduce fuel-consumption. Tis results in a higher payload capacity for commercial aircraſt and better agility for military aircraſt. In terms of productivity, the focus is on the cost of manufacture where fiber laser has the advantage. Te reduc- tion in manufacturing cost significantly impacts the final manufacturing cost of the aircraſt as well as the operation cost. To date, nearly 70% of today’s commercial aircraſt struc-
tures are of aluminum alloys followed by titanium and nickel- based alloys due to excellent strength-to-weight ratio and corrosion resistance. Prima Power Laserdyne has documented its fiber laser welding technology’s successful application to all of these
geometry; and there should be no undercut or concavity of the weld bead. Te ‘top-hat’ beam profile using the Laserdyne 795 high-power fiber laser beam delivery consistently produces welds meeting the required aerospace quality requirements. Titanium and nickel alloys are readily laser weldable, how-
ever special attention must be given to joint cleanliness and gas shielding. Both alloys are highly sensitive to oxidation and subject to interstitial embrittlement (via oxygen, hydrogen, nitrogen, and carbon). Arc and laser welding of these alloys requires the use of an inert shield gas to provide protection against oxidation and atmospheric contamination. Te most frequently used cover gases are argon for titanium alloys and nitrogen for nickel base alloys. When properly cleaned and shielded during welding, tita-
nium and nickel alloys are easily fiber laser welded. Te welds are consistently clean in appearance with low distortion when
When properly cleaned and shielded during welding, titanium and nickel alloys are easily fiber laser welded.
aerospace materials. Te company continues to invest heavily in the development of its fiber laser technology for welding aerospace aluminum, nickel, and titanium alloys. Aluminum alloys have low density. Although their
mechanical properties are lower than those of most steels, they have excellent strength to weight ratio. Tat charac- teristic makes them attractive to the aerospace industry for aircraſt fuselage and wing structures. Te most commonly used aluminum alloys for airframe construction are the age hardening alloys in the 2000 Series. Te 2000 Series (Al-Cu) aluminum alloy series possess high strength but somewhat lower corrosion resistance than most other aluminum alloys. Many of these alloys also have relatively good strength at elevated temperature. When lasers were first tested for welding aluminum
aerospace components in the 1970s and 1980s, deep penetra- tion keyhole welding proved difficult because of the initial high surface reflectivity to the CO2
laser wavelength and high
thermal conductivity of the material. Tis has been overcome by the availability of fiber laser sources with higher average output power and improved focusing systems, producing a power density high enough to produce a stable keyhole for welding aircraſt aluminum. With average output powers exceeding those of Nd:YAG
lasers, fiber laser can extend beyond 8 mm the range of alumi- num thicknesses that can be welded in a single pass. Tis is an important productivity advantage of fiber laser welding. Te quality requirements for welds of aerospace compo-
nents are generally very strict. Tere should be no porosity; the top, middle and bottom weld seam should be of a specified
compared to their arc-welded counterparts. Te fusion zone width and the grain growth are controlled according to laser power at the work piece and welding speed.
Enhancing the Technology To enhance the new fiber laser welding technology for
aerospace applications, Laserdyne has developed new laser beam delivery, wire feed, and process control systems. For ex- ample, the five-axis Laserdyne 795 fiber laser system is being used to weld medium to large 2D and 3D aerospace compo- nents utilizing its unique moving beam motion system. Te system is equipped with a range of focusing and shield gas as- semblies to produce oxide free welds of the desired geometry. Tis third generation BeamDirector, called BD3Y, provides
access to narrow areas for welding fixtured parts. Te clean design of the BD3Y means that there are no hoses or cables to become entangled with the workpiece or fixture. Te BD3Y also provides crash protection to avoid damage to expensive workpieces. Te control used for the laser welding system provides integrated control of the laser, 3D motion, process sensors, wire feeder, and ancillary components. Features such as SPC Data Acquisition log process parameters during weld- ing to provide a permanent record to support qualification of the welding process. Fiber laser welding will extend the application of lasers in
aerospace manufacturing by making laser welding more cost effective compared to conventional joining methods and by providing a single machine tool that is capable of not only welding, but also cutting and drilling. It has a bright future in the new and legacy airframe and aero-engine designs. ✈
Aerospace & Defense Manufacturing 2014 129
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