Process for manufacturing a hollow blade for a turbo-machine

A process for manufacturing a hollow rotor fan blade for a turbo-machine from a plurality of primary parts, including the following steps:

• (a) using computer aided design and manufacture (CAD/CAM) means to create, from a definition of a blade to be produced, a digital simulation of a flat form of primary parts of said blade;
• (b) die-forging said primary parts in a press;
• (c) machining said primary parts;
• (d) depositing diffusion barriers on at least one of said primary parts according to a predefined pattern;
• (e) assembling said primary parts and diffusion welding the assembled primary parts together under isostatic pressure to form a welded assembly;
• (f) inflating the welded assembly of said primary parts using pressurized gas and superplastically shaping said assembly to form a shaped assembly;
• and
• (g) final machining of said shaped assembly;
• wherein said die-forging operation in step (b) is carried out in a hot die at a temperature between 0.7 and 0.8 Tf where Tf is the melting temperature of the material being forged, and with the temperature of the tooling raised to substantially 80% of the temperature of the primary part being forged;
• wherein a blank of each primary part used has a specific trapezoidal shape so as to obtain a final product with a fineness equivalent to about 0.02 times the width of the blade and a working of the metal of the blank which guarantees a grain size sufficient to ensure good diffusion welding conditions in step (e) and desired mechanical characteristics for the finished blade, including good fatigue resistance;
• and wherein when the thickness of the said primary parts, associated with the deformation ratio, is less than a buckling limit thereof, said process includes an additional step of cambering and twisting leading to an elongation of fibres of the material of the primary part enabling the neutral fibre to be brought to a final length thereof on both sides of an axis of the primary part.