Process for local repair of a damaged thermomechanical part and part thus produced, in particular a turbine part
A process and device in production of precise three-dimensional sinters of a shape substantially close to that of an original part, using flash sintering produced by spark plasma sintering (SPS) technology. A mold is produced in a die of an enclosure for SPS flash sintering, the mold being shaped as an impression of the original part. The following are deposited in successive layers in the mold: a layer based on a superalloy powder, a metallic protection layer, and a thermal barrier layer. In a sintering, pressurization is initiated and a pulsed current passes through, producing a rapid rise in temperature in accordance with a flash sintering cycle whose temperature, pressure, and duration are regulated, with at least one temperature plateau and one pressure plateau. The layer of superalloy forms, by diffusion, during the sintering, a bonding continuum of material with the part to be repaired.
1. A process for local repair of a thermomechanical part of a superalloy, comprising:
producing a mold in a die of an enclosure for spark plasma sintering (SPS) flash-sintering, the mold being shaped as an impression of at least a repair portion of the part;
introducing into the mold a layer of brazing powder and at least one layer of a superalloy-based powder constituting a multilayer whole;
then, in a sintering, pressurizing and initiating a passage of pulsed current producing a rapid rise in temperature in accordance with a flash sintering cycle whose temperature, pressure, and duration are regulated, with at least one temperature plateau and one pressure plateau, so that a bond of material with the part can subsequently be produced by diffusion, the sintering producing a preform with composition gradients in the multilayer whole, with a brazing face that can be joined to be in direct contact to the part and a superalloy material appearing on the surface of the preform.
2. The repair process according to claim 1 , in which the temperature, pressure, and duration of the flash sintering cycle are regulated, with a rise in temperature of at least 600° C./min, a temperature plateau substantially in a range between 1000° C. and 2000° C., and a pressure plateau substantially in a range between 10 and 100 Mpa.
3. The repair process according to claim 1 , in which the mold has a shape that corresponds to an impression of an entire original part, and the layer of superalloy forms, by diffusion, a bonding continuum of material with the part to be repaired.
4. The repair process according to claim 1 , in which a metallic protection layer and a thermal barrier layer are deposited on the layer of superalloy during producing the mold.
5. The repair process according to claim 3 , in which, in a subsequent brazing, the brazing face of the preform is placed in contact with an area of the part to be repaired, then, by heating the preform and the part placed alongside in an appropriate furnace to a temperature at least equal to the melting temperature of the brazing alloy, the brazing face is bonded by diffusion of the melting elements of the brazing alloy in the part.
6. The repair process according to claim 4 , in which the metallic protection layer consists of at least one sheet die composed of Ni, Pt, Hf, Y, Si, Cu, Ag and/or Au, and/or of Ni—Al, Ni—Pt—Al and/or Ni—Al—Zr compositions.
7. The repair process according to claim 4 , in which the thermal barrier consists of yttria-stabilized zirconia.
8. A thermomechanical part or a turbine part made of a superalloy repaired according to the repair process of claim 1 via flash sintering, in which the part includes a bond with the part formed by the multilayer whole with composition gradients, obtained by diffusion of a layer of brazing powder and at least one layer of superalloy-based powder.