EP2093021B1 - Method and apparatus for controlled shot-peening of blisk blades - Google Patents

Description

The invention relates to a method for the shot peening of blisk blades with a blasting material thrown onto the blade surfaces with the aid of compressed air or water.

In the shot peening of the surface of workpieces, a spherical blasting medium is thrown with the aid of compressed air at high speed against the workpiece surface to be treated. In the material surface deformed by the shot peening through a plurality of calottes, residual compressive stresses are induced so that the risk of cracking is reduced and fatigue strength is increased. Associated with this are a weight reduction, a work hardening and an increase in service life. Shot blasting is known to have long been used with engine components and here also for blading blades.

Gas turbine rotors, and in particular the rotors of gas turbine engine compressors, are designed with a blading integrally formed on the annular outer periphery of a disk for reliability, weight saving, power enhancement, and durability. Such components are referred to as blisks, the term blisk being a shorthand of the English language term "blade integrated disk". The production of blisks is known to be done by welding, in particular friction welding, separately manufactured blades with the peripheral annular surface of the preferably forged disc or by a proceeding from the outer annular surface of the disc material removal by means of cutting or chemical processes. After forming and finishing the blades, and after the blisk is heat-treated, the blisk blade surfaces can be shot-peened to increase their strength and life by introducing compressive residual stresses into the surface layer.

Irradiation of the arranged at a small distance and also curved and twisted Bliskschaufeln done with a registered from the outside in the blade interstices shot peening. However, the effect of the abrasive jet on the blade surfaces is limited because the blasting agent because of the mutual coverage and thus the insufficient accessibility of the blade surfaces, which is recorded to a greater extent in blisk drums, the surface areas concerned on the one hand only insufficient extent and others are reached at an unfavorable angle and therefore only with insufficient kinetic energy. The surface hardening of the blades is therefore insufficient and uneven. In addition, the blades can be deformed because of the uneven load on the pressure side and on the suction side. By higher jet speeds and larger balls, this disadvantage can not or only partially be resolved, especially as at higher jet pressure and larger balls by the different beam parameters, the risk of blade deformation is still increased and areas with very small radii not processed or filigree blade edges can be damaged.

In another known method for shot peening of blisk blades, the individual blades are arranged in hermetically sealed chambers containing a shot blasting medium set in motion by ultrasound. This method is particularly disadvantageous because of the high cost of sheathing the blades. document WO 2005-065825 shows a method according to the preamble of claim 1.

The invention has for its object to provide a method for shot peening the blades of Blisks or Blisktrommeln that ensures a low and no impairment of the blade shape uniform and high surface hardening of the blades.

According to the invention the object is achieved by a method according to the features of patent claim 1. Advantageous developments and expedient embodiments of the invention are the subject of the dependent claims.

The essence of the invention lies in the separate processing of each individual blisk with simultaneously and immediately opposite and with identical beam intensity and substantially perpendicular to the suction side and the pressure side impinging shot peening, which are guided in adjacent processing paths on the two side surfaces of the respective Bliskschaufel. The beam intensity identical on both blade sides is achieved in that the distance between the jet exit plane and the irradiated surface on both blade sides is substantially the same. With such a shot peening treatment, one in every part of each individual blade becomes one Blisk or Blisktrommel uniform and intense surface solidification achieved, without deforming the blisk blades and in particular their filigree edges in the shot peening treatment. The strength of the blisk blades is increased, so that increases in the fatigue strength and elimination of tensile stresses on the component surface are possible. The risk of cracking is minimized, so that ultimately the life is increased. Due to the uniform, high beam intensity in all surface areas, small-diameter blasting balls can be used, so that even small radii in the transition area to the annulus are detected and hardened by shot blasting.

In an embodiment of the invention, the shot peening (shot blast nozzles) have a rectangular cross-sectional shape and are guided in the longitudinal direction of the blisk blades in adjacent, preferably overlapping processing paths over the two blade surfaces. The overlapping of the machining paths compensates for a lower beam intensity and spherical beam coverage in the edge region of the spherical jet.

An apparatus for carrying out the method according to the invention comprises a double-jet nozzle unit arranged at a movement unit with two elongated jet blast nozzles arranged at a distance and correspondingly adjustable with respect to the respective blade design, which have nozzle openings of the same shape and size arranged laterally at the same height and facing each other. With the aid of the movement unit, the double-jet nozzle unit can be moved with the jet nozzles arranged on both blade sides during processing in the longitudinal direction and in the transverse direction of the individual blisk blades and can also be pivoted about an X-axis and a Y-axis, so that the Shot blasting the scoop surfaces completely capture and also the curved and twisted shape of the blisk blades can follow at a constant distance and all blade areas are treated with substantially the same beam intensity.

The blasting material nozzles and the nozzle openings have a rectangular cross-section or a rectangular Gutaustrittsquerschnitt so that the blade surfaces can be uniformly shot-peened along wide, planar processing paths.

According to an important feature, the nozzle openings are delimited at the free end-side end of the blasting material nozzles by a flat baffle plate arranged at an obtuse angle to the flow direction. At this baffle plate, the blasting balls are deflected outwardly in the direction of the blade surface at an angle equal to or more than 90 °, such that the blade surfaces are predominantly perpendicularly struck by the blasting balls, but also the transition region of the blisk blade to the annulus of the blasting shot is detected. The length of the blasting material nozzles is selected so that the blasting material emerging from the nozzle openings also detects the transition region.

Fig. 1

eine Seitenansicht einer Vorrichtung zum Kugel- strahlverfestigen der Schaufeln einer Bliskt-rom- mel für den Verdichter eines Flugtriebwerks;

Fig. 2

eine Draufsicht auf eine Vorrichtung zur Kugel- strahlverfestigung der Bliskschaufeln einer Blisktrommel;

Fig. 3

einen senkrechten Schnitt durch eine Strahlgut- düse; inkl. Strahlgutführungsstück

Fig. 4

einen waagereichten Schnitt durch die Strahlgut- düse nach Fig. 3; und

Fig. 5

eine detaillierte Ansicht der Strahlgutdüse ge- mäß Fig. 3 im Bereich der Düsenöffnung.

An embodiment of the invention will be explained in more detail with reference to the drawing. Show it:

Fig. 1

a side view of an apparatus for Kugelgeverfestigen the blades of Bliskt- mel- mel for the compressor of an aircraft engine;

Fig. 2

a plan view of a device for Kugelgeverfestigung the Bliskschaufeln a blisk drum;

Fig. 3

a vertical section through a Strahlgut- nozzle; Including grit guide piece

Fig. 4

a horizontal section through the grit nozzle after Fig. 3 ; and

Fig. 5

a detailed view of the Strahlgutdüse according to Fig. 3 in the area of the nozzle opening.

One in the Figures 1 or 2 shown device comprising a plurality of blisks 2 welded together Blisktrommel 3 comprises a moving unit 4, with a attached to a nozzle holder 5 double jet nozzle unit 6 according to the arrows A and B in the vertical direction and in the horizontal direction (see Fig. 1 ) can be moved and pivoted according to the arrow X about a horizontal axis and according to the arrow Y about a vertical axis (see Fig. 2 ) can be.

The double-jet nozzle unit 6 comprises two blasting-material nozzles 7, each designed as flat, rectangular and elongated hollow bodies, which are arranged with their broad sides spaced apart and substantially parallel to one another. The distance between the two Strahlgutdüsen 7 is adjustable and is adjusted depending on the blade thickness-shape and distance so that the Strahlgutaustragsdüsen 7 do not contact the machined Bliskschaufeln 1 or these adjacent Bliskschaufeln during Kugelstrahlverfestigens. The length of the Strahlgutdüsen 7 is greater than the maximum height of the machined Bliskschaufeln 1. The two Strahlgutdüsen 7 have at the front free end in each case a laterally arranged, substantially over the entire width b reaching - rectangular - Nozzle opening 8 on. The closed front end of the nozzle opening 8 and the Strahlgutdüse 7 is formed by an oblique, approximately at an angle of 45 ° extending baffle plate 9, at which the fed via the Strahlgutdüse 7 Strahlgutstrom or the Strahlgutkugeln 10 about 90 ° or larger and thus approximately perpendicular to the longitudinal extent of the Strahlgutdüsen 7 and to the flow direction in the Strahlgutdüsen 7 are discharged via the nozzle opening 8. The nozzle openings 8 of the two Strahlgutaustragsdüsen 7 are directed towards each other and arranged exactly opposite each other.

At the opposite end of the baffle plate 9, the respective Strahlgutaustragsdüse 7 is connected to a Strahlgutführungsstück 11, which in turn is connected to a Strahlgutzuführungsleitung 12 having a substantially circular cross-section. The inner cross section of the Strahlgutführungsstück 11 is formed so that the over the Strahlgutzuführungsleitung 12 by means of compressed air or water supplied jet medium circular cross section of Strahlgutstroms gradually, that is without energy losses and turbulence of Strahlgutstroms and simultaneously increasing the speed of the solidification balls, in a rectangular inner cross section the Strahlgutaustragsdüsen 7 corresponding cross section is transferred.

For the shot peening of the blisk blades 1 of a blisk drum 3 formed and heat-treated by a plurality of blisks 2 welded together, the double-jet nozzle unit 6 is moved in a plurality of overlapping paths in the longitudinal direction of the blisk blade 1 to be individually processed by means of the movement unit 5. The overlapping of the processing paths is required because the emerging at the edges of the nozzle opening 8 blasting material is slightly lower than in the Center. The Bliskschaufel 1 is located during processing centrally between the two set at a distance corresponding to the cross-sectional profile of the respective Bliskschaufel Strahlgutdüsen 7, so that on the suction side and the pressure side of the Bliskschaufel 1 each opposite surface areas with a due to the central arrangement on both sides the same strong ball jet are acted upon and thus no deformation of the Bliskschaufeln 1 by unilateral or different strength in the action of the shot peening is recorded. When the double-jet nozzle unit 6 is moved along the machining paths, the double-jet nozzle unit 6 is pivoted in accordance with the arrows X and / or Y so that the jet discharge plane follows the opposite nozzle openings 8 of the rotated blade shape and is oriented substantially parallel and equidistant from the blade surface.

The balls essentially meet vertically and thus with maximum utilization of their impact energy on the surfaces to be machined. As a result, the blasting material balls can have a comparatively small diameter, so that even areas with small radii, for example in the transition region between the lateral blade surfaces and the annulus, can be processed with the radiation medium and hardened by shot blasting. Due to the individual processing of the blisk blades, in which blasting shot with small diameter substantially perpendicular and impact with the same strength only on the side surfaces, in particular a deformation of the filigree formed, particularly easily deformable blade edges is prevented. With the method described above, each individual Bliskschaufel on the pressure side and the suction side is processed with the same beam intensity and fully shot-peened solid. The case in the surface layer on both sides evenly induced compressive residual stresses cause an increase in strength and a reduction in the risk of cracking, so that the life of the blisk blades is increased. On the other hand, due to the increase in strength, material can be saved and the weight reduced.

LIST OF REFERENCE NUMBERS

1

blisk blade

2

blisk

3

blisk drum

4

moving unit

5

nozzle holder

6

Double nozzle unit

7

Strahlgutdüse

8th

nozzle opening

9

flapper

10

Strahlgutkugeln

11

Strahlgutführungsstück

12

Strahlgutzuführungsleitung

Claims (6)

1. Method for strengthening the surface of BLISK blades integrally formed onto a rotor by means of a pressure medium applied to the blade surfaces, characterized in that each BLISK blade is separately processed along side-by-side processing paths, simultaneously on the pressure and on the suction side of the BLISK blade, on immediately opposite surface portions using shot streams which essentially vertically strike the processing surface and essentially feature identical peening intensity, with the shot streams being produced by compressed air and exiting from a dual-nozzle unit, which is moveable and swivellable along the two blade surfaces.
2. Method in accordance with Claim 1, characterized in that the shot streams exiting from the dual-nozzle unit and impinging on the two blade surfaces each feature a rectangular cross-section, with an initially circular shot stream being accelerated and transformed in the dual-nozzle unit.
3. Method in accordance with Claim 1, characterized in that the successive processing paths overlap on the respective blade side to compensate for the lower peening intensity of the shot stream in the edge areas.
4. Method in accordance with Claim 1, characterized in that the distance between the shot exit plane on the dual-nozzle unit and the processing surface is essentially equal on both blade sides in order to achieve identical peening intensity on both sides.
5. Method in accordance with Claim 1, characterized in that the spherical shot of the two shot streams exit from the dual-nozzle unit essentially vertically and hit the blade surfaces to be processed at an essentially right angle.
6. Method in accordance with Claim 1, characterized in that the shot size in the shot streams is selected such that even very small gorge radii are reached by the shot-peening medium and strengthened by shot-peening.

Images