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Electron-beam welding of precipitation hardened nickel-base superalloys - assessment of weldability using metallurgical methods

: Busch, W.-B.; Kunze, H.-D.

4th International Colloquium on Welding and Melting by Electron and Laser Beams. Vol.1
S.235-242 : Abb.,Tab.,Lit.
International Colloquium on Welding and Melting by Electron and Laser Beams <4, 1988, Cannes>
Fraunhofer IFAM ()
electron beam welding; heat affected zone; microhardness; microstructure; Udimet 700; welding defect

For precipitation hardened nickel-base alloys the area next to the fusion line is of great importance because of the microstructural changements and formation of microcracks. In the weld metal and the zone next to the fusion line the temperature is high enough to dissolve all particles, but during cooling the -phase reprecipitates spontaneously. In simulation tests the relationship between temperature gradients and particle size could be described: at low cooling rates which are characteristic for furnace cooling processes coarse and cubic particles are formed, at high cooling rates being typical for weldments only very small and round precipitates can be found. After welding the formation of cracks is possible. The number of cracks seems to be correlated with the heat treatment of the material.