Method of repairing a blisk and test pieces by welding

1. A method of repairing a turbomachine one-piece bladed disc or blisk having at least one damaged zone, by build-up of metal in said damaged zone by means of a laser build-up welding machine, comprising:

preparing the damaged zone by machining the damaged zone so as to obtain a zone of defined profile to be repaired;

preparing a start-of-run test piece by machining a test zone, the test zone including the defined profile such that the test zone in the start-of-run test piece has the same geometry as the machined damaged zone in the blisk;

build-up welding of the start-of-run test piece using the laser build-up welding machine, the operating parameters of the laser build-up welding machine being preset;

validating the operating parameters of the laser build-up welding machine by checking a geometric quality and a metallurgical quality of the test piece and determining if the test piece meets criteria for acceptance;

build-up welding of the zone to be repaired of the blisk using the laser build-up welding machine with the validated operating parameters; and

re-working the repaired zone.

2. The method according to claim 1 , further comprising, after build-up welding the zone to be repaired of the blisk, preparing an end-of-run test piece by machining a test zone, the test zone including the defined profile such that the test zone in the end-of-run test piece has the same geometry as the test zone in the start-of-run test piece and the machined damaged zone in the blisk,

build-up welding the end-of-run test piece, and

checking the geometric quality and the metallurgical quality of the end-of-run test piece.

3. The method according to claim 1 , wherein the constituent metal of the disc is a titanium alloy.

4. The method according to claim 3 , wherein the build-up weld metal is the titanium alloy.

5. The method according to claim 3 , wherein constituent metal of the disc is Ti17 or TA6V.

6. The method according to claim 1 , wherein the damaged zone is located on an aerofoil tip.

7. The method according to claim 1 , wherein the damaged zone is a leading-edge corner or trailing-edge corner of an aerofoil.

8. The method according to claim 1 , wherein the damaged zone is located on a leading edge or trailing edge of an aerofoil.

9. The method according to claim 1 , wherein the build-up welding is performed by melting a filler metal by a laser beam.

10. The method according to claim 1 , in which the disc has at least two damaged zones, said two zones being repaired after treatment of the start-of-run test piece.

11. The method according to claim 1 , further comprising regulating the build-up welding installation, during which regulating the operating parameters are preset, by build-up welding a regulating test piece, and checking geometric quality and metallurgical quality of the build-up weld by at least one of non-destructive or destructive testing.

12. The method according to claim 11 , wherein the test piece has a profile of a zone to be build-up welded of a leading edge or trailing edge of an aerofoil of said disc.

13. The method according to claim 12 , wherein the checking metallurgical quality by at least one of non-destructive or destructive testing includes a fatigue test carried out on a test specimen machined from the test piece after the build-up welding.

14. The method according to claim 11 , wherein the regulating test piece is cut from a forged blisk blank.

15. The start-of-run test piece for implementing the method according to claim 1 , wherein the test piece includes a titanium alloy, and the shape of which test piece simulates the tip of an aerofoil with a sealing lip.

16. The start-of-run test piece for implementing the method according to claim 1 , wherein the test piece includes a titanium alloy, and the shape of which test piece simulates a leading-edge or trailing-edge corner of an aerofoil tip machined according to said defined profile.

17. The method according to claim 1 , wherein the laser build-up welding machine includes a nozzle, the nozzle including a plurality of channels which feed a metal powder that is deposited on the zone to be repaired along a laser beam propagation axis.

18. The method according to claim 17 , wherein the build-up welding comprises progressively building up a stack of layers of material deposited on the zone to be repaired by moving the nozzle of the laser build-up welding machine forward and backward along the zone to be repaired, and the build-up welding is performed at a constant speed and intensity.

19. The method according to claim 1 , wherein the defined profile includes a curved portion and a straight portion connected to the curved portion.