Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Laser welding of superalloys and of titanium alloys

The operating temperature of jet engines has gradually increased by some 15 C per year, making design of turbine engines very difficult. It is necessary to use superalloys and titanium alloys in aeronautic and aerospace structures. Laser are a convenient alternative for welding even complex-shaped components made of these alloys. Microanalyses were performed using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and optical microscopes. The weldability ranges of optimized joints were obtained in the first half of the project on different thicknesses of the superalloys Hastelloy X, Inconel 718, Nimonic C263, corresponding to the industrial components which were subsequently welded in the second half of the project. As a consequence of the evolution of the microstructure with the post weld heat treatment the fatigue test were devised. Fatigue test were performed on specimens Cosmetic runs on two sides greatly improved the fatigue resistance of the joints, while the improvement is less significant when the run is only on one side when comparison is made with welded joints.

The lasers were used to weld an exhaust frame for CFM 56 engine. Both carbon dioxide or neodymium yttrium aluminium garnet lasers can be adopted in the manufacturing of this component. A bearing support for an aeroengine was built, the cone being joined along the generatrix using a laser. Helium was used as shielding gas on both sides, and a new nozzle was developed for this high-power application. The shielding action resulted in a very shiny appearance of the weld. The result met the quality specifications set by the manufacturer. The manufacture of lightweight spherical reservoirs involved two half-shells being welded together along their equator, the joint being sputtering-free inside the reservoir and smooth on the outside. Welding was performed using a Rofin Sinar RS 6000 carbon dioxide laser, on the same station the smoothing of the bead was achieved by cosmetic runs.


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