Construction element having a bond structure for a turbo engine, method for the production of a construction element having a bond structure for a turbo engine, and turbo engine having a construction element having a bond structure

A construction element, particularly adapted and configured for use in a turbo engine, in particular an aircraft engine, wherein a bond coat having a bond structure and thereabove a ceramic coat are disposed on a base. The lateral faces of the bond structure in the cross section are configured so as to be free of undercuts, wherein peak structures and/or trough structures are present, and the peak of the cross section of a peak structure has a mean peak angle (α) of less than or equal to 90°, most particularly less than 45°, and/or the trough structure has a valley angle in the range 90°≤β<170°.

REFERENCE TO A RELATED APPLICATION

This application claims priority to German Patent Application No. 10 2018 119 608.3 filed on Aug. 13, 2018, the entirety of which is incorporated by reference herein.

BACKGROUND

The disclosure relates to a construction element having a bond structure for turbo engines, to a method for the production of a construction element having a bond structure for a turbo engine, and to a turbo engine having a construction element having a bond structure.

Very high operating temperatures are reached in turbo engines such as, for example, aircraft engines or stationary steam or gas turbines. In excess of 2000 K can be reached in modern aircraft engines, for example. On account thereof, specific parts of the turbo engine such as, for example, combustion chambers or the intake region of the turbine in an aircraft engine, are subjected to very high thermal loads. Furthermore, these construction elements have additionally to resist high mechanical loads in particular when starting-up a turbine, since the tips of the turbine blades at least briefly come into contact with the turbine wall.

It is therefore known for specific parts of the turbo engine to be covered with a mechanically stable, heat-resistant, multi-layer coat. Such a multi-layer coating is known from EP 1 491 658 A1, for example. A so-called metallic bond-coat layer (adhesion promoting layer) is applied to a metallic substrate, a ceramic coat in turn being applied to said bond-coat layer. These two coats conjointly are also referred to as a thermal barrier coating (TBC). DE 10 2005 050 873 A1 and DE 10 2011 085 801 A1 relate to structured high-temperature coatings.

SUMMARY

It is therefore expedient for thermally and mechanically stable construction elements which are capable of being reliably connected to a high-temperature coating to be developed, wherein the production of the construction element has to be economical.

The object is achieved by a construction element having features as described herein.

The construction element has a base on which a bond coat having a bond structure is disposed. A ceramic coat is disposed on top of the bond coat.

The lateral faces of the bond structure in the cross section are configured so as to be free of undercuts, wherein peak structures and/or trough structures can be present.

The peak of the cross section of a peak structure has a mean peak angle α in the range α≤90°, particularly α≤45°. The trough structure has a valley angle β in the range 90°≤β<170°.

Free of undercuts means that the cross-sectional width of the bond structure decreases in a monotonous manner, particularly a steadily monotonous manner, to the peak. A peak structure has individual peaks protruding from a base area, or a tapering rib. A trough structure has individual depressions in a base area. In principle, it is possible for peak structures and trough structures to be combined with one another.

Such a bond structure can be produced from the bond coat in particular by an ablative laser machining method, this being more economical than a production by a laser deposition method, for example.

The height of the bond structure is measured from the surface of the bond coat from which the bond structure has been machined, for example. The height of the bond structure in the case of a trough structure herein is measured from the floor area. The ratio of the thickness of the bond coat to the height of the structure can thus be 0.1 to 10, particularly 0.3 to 3.

Additionally or alternatively, the ratio of the height of the bond structures to the mutual spacing of the bond structures in one embodiment can be in the range from 0.1 to 5, particularly between 0.3 and 3.

In one embodiment, the construction element can have a structured surface having a nominal roughness Ra(mean roughness) between 5 μm and 25 μm.

Embodiments of the construction element can have bond structures as a linear structure, as a punctiform structure, as a mesh structure, as a honeycomb structure, and/or as a corrugated structure from mutually parallel-running corrugations. In principle it is possible for the forms of the structures to be combined with one another. For example, a linear structure and a punctiform structure can thus be combined with one another by superimposition. The bond structures herein can also follow complex surfaces. The height of the cross section of the bond structure along a spatial extent, for example in a linear mesh structure, of the bond structure can be substantially consistent so that a type of wall having a consistent height is present, for example.

The maximum height of the cross section of the bond structure at crossover points of the bond structure, particularly in a mesh structure, can vary, particularly as compared to the height of the bond structure outside the crossover points. For example, a mesh-type bond structure in which particularly high peaks or deep troughs can be present at the crossover points would thus be present.

In one embodiment, the mean spacing between peaks of the bond structure is between 50 and 5000 μm. In the case of a mesh structure, this would be the spacing between two rows of the mesh. The ratio of 0.1 to 5 for the height of the structures to the spacing of the structures is characteristic for the structures.

In one embodiment, the construction element has a bond structure having a substantially triangular cross section, particularly an isosceles triangular cross section. These cross sections, for example of linear bond structures in meshes, can be simply produced and offer a sufficiently large surface area for promoting bonding to the ceramic coat.

The width of the cross section of the bond structure herein can decrease uniformly from the surface of the bond coat to the peak. A uniform decrease in width can be understood to be, for example, a linear decrease (side of the triangle) or an exponential decrease in width. The decrease in width can also be composed of a sequence of segments (lines, arcuate segments) free of undercuts.

A particularly simple construction is present when the cross section of the bond structure is symmetrical to a perpendicular line through the peak of the bond structure or to the vertical central axis of the trough.

In one embodiment, the ratio of the height of the cross section to the width at the base of the bond structure can also be between 0.1 and 10, particularly between 1 and 5. The height of the cross section of the bond structure can also be between 50 and 500 μm, particularly between 70 and 150 μm. In principle, the dimensional indications are based on mean values.

Furthermore, in one embodiment the height of the cross section of the bond structure along the bond structure can be substantially consistent.

The ceramic coat can comprise at least one oxidic ceramic, particularly containing magnesium spinel and/or aluminium oxide, particularly yttrium-stabilized zirconium oxide (YSZ), pyrochlores, or perovskites.

The object is also achieved by a method having features as described herein. A bond coat having a bond structure is applied to a base herein, and a ceramic coat is disposed thereabove.

The bond structure herein is generated by a laser ablation method so as to be free of undercuts.

The ceramic coat, particularly a YSZ coat and/or a magnesium spinel coat, can be applied by an atmospheric plasma spray method, for example.

Alternatively, a YSZ coat can be applied to the bond coat by an atmospheric plasma spray method, and a magnesium spinel coat can be applied thereabove by a suspension plasma spray method.

The object is also achieved by a turbo engine having features as described herein, wherein the construction element is configured as part of a combustion chamber, as part of a wall of a turbine, and/or is configured in the intake region of a high-pressure part of a turbine.

DETAILED DESCRIPTION

An aircraft engine20as an exemplar of a turbo engine is illustrated in part inFIG. 1, temperature-resistant construction elements10(to be described hereunder) having a structured bond coat2(seeFIG. 2 or 3, for example) being able to be used in said aircraft engine20. The axially rear part of the aircraft engine20is illustrated here, that is to say that the compressor stages of the aircraft engine20are not illustrated.

Particularly high thermal loads are present in a combustion chamber21. For this reason, plate-shaped construction elements10having a bond structure4(seeFIG. 2 or 3, for example) can be disposed in the interior of the combustion chamber21.

The highest temperature is present at the exit of the gases from the combustion chamber21and at the entry into a high-pressure stage22of the turbine. Additionally or alternatively construction elements10can therefore be disposed in the high-pressure stage22. Said construction elements10herein are not configured as plates, but the coating is disposed directly in the region of the stator of the turbine, for example. The region of the stator per se thus becomes the coated construction element10. In principle, it is also possible for the coated construction elements10to also have ducts or openings for cooling media.

It is furthermore also possible for blades of rotors and/or stators to be provided with the coating so that said blades become construction elements10in the context of the present description.

A further possibility lies in using the construction element10as a coating, that is to say as a so-called liner23, in the wall of the turbine wall, that is to say particularly in those regions that are opposite the blades of the rotors. Liners23can be used in the regions in which rotor blades, for example of the turbine, are at least temporarily in mechanical contact with the wall of the casing. This is quite desirable at least for minimizing the gap between the wall and the turbine blade. The construction elements10having bond structures4and a ceramic coating3do not only have a high thermal load bearing capability, but in mechanical terms are also configured such that said construction elements10can be used as liners23.

Liners23can also be used in combustion chambers, or the coating can become directly part of the combustion chamber wall.

In principle, the construction element10can be used at those locations where comparatively thick ceramic coats are usually disposed.

By way of the embodiments described here it is possible for a fine structuring to be applied directly to a bond coat material without compromising the metal base. Only minor thermal gradients within the construction elements10arise in operation. The adhesion of the bond coat on the base material1is also very positive. Said embodiments also have a high resistance to oxidation.

A sectional view through the surface of an embodiment of a construction element10is schematically illustrated inFIG. 2.

A bond coat2having bond structures4herein is disposed on a base1. The structuring in the embodiment illustrated is composed of a three-dimensional mesh structure (seeFIG. 4, for example) of which only the cross-sectional faces of three mesh elements (the bond structures4) are illustrated in the sectional view ofFIG. 2.

The bond structures4here are configured so as to be integral to the bond coat2, since the bond coat2has been machined by an ablative laser method. This means that the bond structures4have been machined from the bond coat2such that said bond structures4extend vertically from the surface of the bond coat2. This is referred to as a peak structure since the peaks6rise above a base area.

The cross-sectional faces of the bond structures4here are configured so as to be substantially triangular, wherein the two lateral faces5of the bond structure4here are configured so as to be of equal length; a symmetrical shape is present, wherein the axis of symmetry points from the peak6perpendicularly towards the base1.

The angle α at the peak6of the bond structure4here is approximately 40°. The angle is measured from the peak6, between the lateral faces5.

The peak angle in alternative embodiments can be α≤90.

Furthermore, the lateral faces5are configured here so as to be straight, that is to say that there are particularly no undercuts.

A ceramic coat3, for example from YSZ (yttrium-stabilized zirconium oxide) and/or magnesium spinel, is disposed above the bond coat2.

The bond structure4having the inclined lateral faces5without undercuts offers a positive connection to the ceramic coat3, wherein the peaks6of the bond structure4can ensure a targeted segmentation in the ceramic coat3.

In the case of the targeted segmentation, cracks7are induced in the ceramic coat3so as to achieve a mechanical relaxation of tension. Said vertical cracks7can be configured in a particularly efficient manner when the bond structure4in an undercut-free manner tapers towards the top, that is to say towards the peak6.

The height H of the bond structure4, measured from the surface of the bond coat2, is between 50 and 500 μm; the height H in the embodiment illustrated is approx. 100 μm. The ratio of the height H to the width B at the base of the bond structure4(that is to say on the surface of the bond coat2) here is 1.25. Alternatively, the H-to-B ratio can be in the range between 1 and 10.

The embodiment according toFIG. 3represents an alternative to this embodiment so that reference can be made to the relevant description ofFIG. 2.

Here too, the width B of the cross section of the bond structure4decreases in a monotonous manner from the base on the surface to the bond coat2towards the peak6. However, the lateral walls5here are in each case curved towards the inside. However, in both cases the cross sections of the bond structure4are symmetrical to the perpendicular line through the peak6.

It is to be pointed out that the geometric ratios stated here cannot fully mirror the reality in terms of production technology, such as is illustrated by means of the following figures, for example. The numerical values in particular are thus to be understood as mean values, since there are always production-related deviations.

A further embodiment of an undercut-free bond structure is illustrated inFIG. 4, specifically a trough structure, that is to say that individual troughs8are incorporated in a base area of the bond coat2. The troughs8have in each case a substantially square or rectangular floor area, wherein the flanks rise from the floor area towards the base area of the bond structure2. The angle of the flanks in relation to the floor area is the valley angle β of the trough8. Said valley angle β herein can be between 90 and 170°. A valley angle of β=90° would correspond to vertical walls. In the case of trough structures, the ratio of the height H of the cross section to the width B at the base of the bond structure4can also be less than one so that a range between 0.1 and 10 is possible in terms of the ratio.

A first embodiment for a mesh-type bond structure4, in which a bond coat2from CoNiCrAlY—after being applied to the base not illustrated inFIG. 4—is structured by an ablative laser method is illustrated inFIG. 5(confocal laser microscope image). A ceramic coating2from YSZ and magnesium spinel is applied to the bond coat2by an atmospheric plasma spray method.

Some of the parameters of the laser ablation method for the production of the bond structure are listed below:laser output: in the kW range at peak output (the examples illustrated have been generated by a Trumph TruMark 5020 Laser (Nd:YAG) at a wavelength of 1062 nm);pulse length in the range of 100 nanoseconds;frequency of a few 100 kHz, in particular a few 10 kHz;beam diameter (a few 10 μm);number of the sequential pulses in the range from 2 to 10;incorporating the bond structures by way of a meandering program.

The bond structures4here are configured as a mesh in which the mesh lines intersect one another in a substantially orthogonal manner. The lateral lengths of the mesh cells are substantially identical so that a square structural pattern is created. The maximum height Hmax of the cross section of the bond structure4at the crossover points of the mesh lines of the bond structure4is greater than the height H of the bond structure4outside the crossover points. The height H of the mesh structure4is substantially consistent between the crossover points.

The deviations from the idealized illustration ofFIGS. 2 and 3become evident in the high-resolution illustration ofFIG. 5. However, it can be seen that the bond structure4in the cross section is without undercuts, and the peak angle α is less than 90°. This can likewise be clearly seen in the sectional image ofFIG. 6(SEM picture). The section plane here is perpendicular to the mesh lines. The peak angle α of the bond structure4is plotted at one location.

A SEM sectional picture through another embodiment of a construction element10is illustrated inFIG. 7. Only the SPS-Mg-spinel coat is illustrated herein.

Here too, a bond coat2from CoNiCrAlY is machined by an ablative laser method in order to generate an undercut-free bond structure4which has a mean peak angle of less than 90°.

A YSZ coat is applied to the bond coat2by an atmospheric plasma spray method. A magnesium-spinel coat which already has a specific degree of segmentation is then applied by a suspension plasma spray method (SPS). The ceramic coat3here thus comprises two layers from different materials.

The use of an ablative laser method for structuring is favourable in economic terms. It is also not necessary for complex peak structures to be shaped.

Different bond structures4are illustrated inFIGS. 8A to 8F. The bond structures4are particularly intended for preventing the ceramic high-temperature coating3from flaking in large areas. Also, cracks in the high-temperature coating3cannot extend in an arbitrary manner in the horizontal direction. The bond structures4here in can cross one another or be disposed so as to be mutually parallel.

A bond structure4which is formed from parallel linear elements is illustrated inFIG. 8A. The spacing L between the peaks6herein is between 500 and 5000 μm. However, bond structures4do not mandatorily have to comprise only linear elements.

A corrugated bond structure4from curved elements that lie so as to be mutually parallel is illustrated inFIG. 8B. Here too, the spacing L between the elements is between 500 and 5000 μm. A propagation of cracks can be particularly effectively suppressed in the case of an amplitude of the corrugated structure which is greater than the spacing L between the structural elements.

An embodiment in which the elements intersect one another is illustrated inFIG. 8C. A mesh structure as is illustrated inFIG. 5, for example, is created, wherein the spacing L between the parallel elements (that is to say between the peaks) is between 500 and 5000 μm.

A honeycomb-shaped pattern which is constructed from linear elements is illustrated inFIG. 8D. The spacing L between two parallel elements is between 500 and 5000 μm.

A punctiform pattern such as is present in a peak pattern, for example, is illustrated inFIG. 8E. The peak pattern here in can readily be configured so as to be regular, as is illustrated inFIG. 8E, or else random, as inFIG. 8F.

In principle, it is possible for a plurality of differently shaped undercut-free bond structures4and/or else patterns to be disposed on a construction element10. The spacing L in a pattern can thus particularly be varied so as to ensure an optimal adaptation of the component10to thermal loads.

In principle, it is also possible for the patterns, for example the patterns illustrated inFIGS. 8A to 8E, to be combined with one another.

LIST OF REFERENCE SIGNS

1Base2Bond coat3Ceramic coat4Bond structure of the bond coat5Lateral faces of the bond structure6Peak of the cross section of a peak structure7Crack in the ceramic coat8Trough of a trough structure10Construction element20Aircraft engine (turbo engine)21Combustion chamber22High-pressure stage of a turbine23Linerα Peak angle in the cross section of a peak structure of the bond structureβ Valley angle in the cross section of a trough structure of the bond structureB Width of the cross section of the bond structureH Height of the cross section of the bond structureHmax Height of the cross section of the bond structure at crossover pointsL Spacing between peaks of a bond structure