EP1071831B1 - Method for producing fibre reinforced metallic components - Google Patents

Abstract

The invention relates to a method for producing fibre reinforced metallic components having a complex geometry. Metal-coated SiC-fibres are connected with each other and with the component by means of pressure influence at a high temperature in a vacuum and in a positive material fit. The inventive method comprises the following steps: A) SiC-fibres (5) are mounted on a profile piece (2) having a simple geometry. Said SiC-fibres are held by means of a metallic counterpart (8) without exerting a force. B) The unity made of the profile piece, the fibres and the counterpart is plastically formed into the complex final shape between form tools (12, 13) by exerting a pressure at an increased temperature in a vacuum, whereby the fibres do not have a positive material fit with each other or with the metallic component. C) The formed unity is further packed and consolidated in a metallic and positive material fit between the form tools by further increasing the pressure or the temperature.

Description

The invention relates to a method for producing fiber-reinforced metallic Components with complex, spatial geometry, according to the generic term of Claim 1.

The exceptional strength properties of SiC fibers are well known. In conjunction with their thermal resilience, these predestine the ceramic SiC fibers as reinforcing elements for metallic materials. With regard to an intimate, load-transmitting connection between the ceramic fiber and the metallic matrix, the fiber must be provided in advance with a firmly adhering surface coating made of a metal which is identical or at least "related" to the component material, with regard to the subsequent diffusion connection / welding. The fibers are usually coated using the PVD process, especially using magnetron sputtering. The metal components, ultimately resulting fiber reinforced be called (omposites M etal M atrix C) as "MMC's". SiC fibers are produced as long or "endless fibers" with lengths of up to about 40 km, with fragments / sections of, for example, 150 m length being processed in construction practice. A preferred fiber diameter is about 100 microns. A certain disadvantage of the stiff SiC fiber is its kink sensitivity, which is why it can only be bent with relatively large radii. The minimum bending radius for said 100 µm fibers is approximately 2.5 cm. Due to the large fiber length, it is possible to apply these advantageously to components to be reinforced using winding technology, of course, taking into account the fiber-specific minimum bending radius. Up until now, mainly geometrically relatively simple rotor elements have been mentioned as concrete applications, for example in the form of rotationally symmetrical shafts, disks and rings or combinations of these elements. Manufacture is usually to be carried out in such a way that metallic supports with a contour that at least largely corresponds to the final shape are wound with a metal-coated SiC long fiber, the fiber windings are covered with metal, and the unit thus prefabricated is monolithically bonded, ie consolidated, in vacuo by the action of pressure and temperature are, the latter preferred in the "HIP" process ( H ot I sostatic P ressing). In addition to contoured components, such as lids, sleeves, tubes, discs, etc., flexible or pourable elements, such as foils, wires, powder, etc., can also be used as cover for the fibers. Due to the favorable strength / weight ratio, titanium and its alloys occupy a preferred position among the metals to be reinforced.
See, for example, DE-PS 43 24 755.
For higher operating temperatures, metals such as nickel and cobalt are suitable as matrix materials. Due to the high strength of the SiC fiber and due to its relatively low density (approx. 3.9 g / cm ³ ), SiC fiber-reinforced components are practically always easier to build than corresponding components that consist only of metal. This in turn predestines "MMCs" with SiC reinforcement for use in high-speed rotors of all kinds. The currently achievable fiber content in the reinforcement area is around 40% by volume.

The problem of manufacturing MMC components has not yet been satisfactorily resolved with SiC fiber reinforcement in complex, three-dimensional geometries, e.g. in the form of engine blades. On the one hand, spatially complex shapes can be created Metal carrier - as a preliminary component - practically not defined with the "stubborn" SiC fibers occupy, especially not in the preferred winding technique. On the other hand, consolidated SiC fibers, their metallic surfaces have already established integral connections, de facto no longer permanent deform, unless fiber breakage / destruction.

Proceeding from this, the object of the invention is to provide a method for producing SiC fiber-reinforced metallic components which, in particular in the case of more complex, three-dimensional geometries, enables the production of defined fiber reinforcements in a reproducible and economical manner and thus the application of the MMC technology to complex shapes Makes components really useful for the first time.
This object is achieved by the method steps A to C characterized in claim 1, in conjunction with the generic features in its preamble.

The principle of the invention is that the fiber reinforcement on a metallic Profile piece applied with simple geometry and by means of a metallic counterpart is held that the unit of profile piece, fibers and counterpart with still "loose" fibers plastically formed into the complex final shape and only then then consolidated into a monolithic part. The steps of the plastic Forming and consolidation run at least largely separately one after the other in the same device / within the same molds, the Process parameters pressure, temperature and time can be controlled accordingly. After consolidation, there is usually no finished component, so that further manufacturing steps, e.g. cutting or joining technology, connect.

Advantageous refinements of the method according to the Main claim marked.

Figur 1

einen Querschnitt durch ein faserbelegtes Profilstück mit Gegenstück,

Figur 2

einen Schnitt durch zwei Formwerkzeuge mit einer noch zu verformenden Einheit,

Figur 3

ein Diagramm mit dem zeitlichen Druck- und Temperaturverlauf bei der Umformung und Konsolidierung sowie einen mit Figur 2 vergleichbaren Schnitt mit einem umgeformten und konsolidierten Teil,

Figur 4

einen drehbaren Träger mit mehreren, faserbewickelten Profilstücken,

Figur 5

zwei konsolidierte, zu einem hohlen Schaufelblatt zu verbindende Teile, und

Figur 6

das aus den Teilen gemäß Figur 5 gefügte Schaufelblatt.

The invention is subsequently explained in more detail with reference to the drawings. In a simplified, rather schematic representation:

Figure 1

a cross section through a fiber-coated profile piece with counterpart,

Figure 2

a section through two molds with a unit to be deformed,

Figure 3

1 shows a diagram with the pressure and temperature curve over time during the shaping and consolidation, and a section comparable to FIG. 2 with a deformed and consolidated part,

Figure 4

a rotatable carrier with several, fiber-wound profile pieces,

Figure 5

two consolidated parts to be connected to a hollow airfoil, and

Figure 6

the blade made from the parts according to FIG. 5.

The geometrically simple, metallic profile piece 1 in Figure 1 is of a U-profile formed with a flat base and with low, vertical legs. It is already with metal-coated SiC fibers 4 - more precisely with pieces of one or a few SiC long fibers - occupied and should by means of the lid-like, metallic Counterpart 7 "closed", for which the latter e.g. by spot welding is fixed on the legs of the profile piece 1. The counterpart 7 the SiC fibers 4 are to be held in their nominal position as freely as possible so that the metallic ones Fiber surfaces still with little friction relative to each other and relative to adjacent profile surfaces remain longitudinally displaceable, what for later forming important is. The voids between the fibers can - at least partially - can be filled with metal powder (not shown), causing subsequent consolidation may be facilitated and improved.

Figure 2 shows a still flat unit 10 made of profile piece 2, SiC fibers 5 and counterpart 8, which between two molds 12, 13 with the same convex / concave curved contact surfaces is inserted. The forming tools 12, 13 belong to a - not shown - hot press, the work space can be evacuated and heated (sign "T" for temperature). The arrows above and below the molds 12,13 including the characters "p" symbolize the pressure, whereby at least one mold in the direction of the arrow - and vice versa - designed to be movable is. The here shown simply curved for clarity Contact surfaces of the molding tools 12, 13 usually become more complex in reality, have three-dimensional shapes, such as those found in gas turbine engine blades required are.

FIG. 3 shows a diagram on the left with the curves of pressure (p) and temperature (T) over time for the two process steps "forming" and "consolidation", which are carried out in succession in the same device. The curves pressure and temperature tend to be uniform, which is not always the case have to be.

Starting from the state recognizable in FIG. 2 with the molds still open 12.13 and after reaching a tool and workpiece temperature, at the metal parts of the unit 10 are easily plastically deformable, the Forming tools 12, 13 moving towards one another with a defined pressure / defined force, until the unit 10 is completely plastically formed, i.e. all over the Contact surfaces of the molds 12,13 is present. During this deformation process The metal-coated SiC fibers 5 must not yet be with one another or with glue / weld the adjacent parts 2.8 because the resulting parts high shear stresses hinder the deformation or lead to fiber breakage would. Therefore, pressure p and temperature T must not be too high here. In the p-T time diagram, this forming step is in the form of the two lower ones To recognize plateaus.

After the plastic forming has ended, that is to say after the movable molding tool has come to a standstill with unchanged pressure, the pressure and the temperature are increased further in order to initiate the consolidation step in which, with further structural compression by diffusion bonding / welding of the inner metal surfaces, a monolithic , largely "cavity-free" part with load-bearing integrated fiber reinforcement. This state with the final compressed, consolidated part 11 is shown on the right in FIG. 3. In the pressure-temperature-time diagram, the consolidation corresponds to the two broad upper plateaus.
It may be sufficient to increase only one of the parameters p, T for the transition from plastic forming to consolidation. Experimental investigations are certainly indispensable for this.
It is obvious that the part 11 generally does not yet represent a finished component after removal from the molds 12, 13.

FIG. 4 shows a particularly economical method for simultaneously cutting several profile pieces 3 to be provided with a fiber assignment. However, this sets one - in the initial state - Unidirectional fiber orientation ahead. The "trick" is to arrange a plurality of profile pieces 3 on the circumference of a wheel-shaped, rotatable carrier 14, that the target grain direction of each profile piece 3 is tangential. The Profile pieces 3 can be flat or - relatively simply - curved. By rotating the carrier 14 and wrapping it with at least one long tangential one fed SiC fiber 6 after a certain number of revolutions and a controlled lateral displacement of the fiber feed, i.e. a helical one Wrapping in several layers if necessary, the desired occupancy achieved. Then the metallic counterparts 9 are applied and fixed, so that the SiC fibers are captured. This state - with the carrier 14 standing - is shown in FIG. 4 reproduced (the rotation arrow around the carrier axis is therefore only dashed). Now the free-standing fiber strands can be severed between the profile pieces 3 and cut back to the component ends so that the units made of profile pieces, fibers and counterparts separately from the carrier 14 are. Then, as already explained, each unit is plastically reshaped and consolidated.

It is also conceivable to design the molds from FIGS. 2 and 3 in such a way that Several, prefabricated units - each consisting of a profile piece, fibers and counterpart - plastically formed together, consolidated and possibly also together be connected, the units side by side / one behind the other and / or arranged one on top of the other between the molds.

Figures 5 and 6 relate specifically to the manufacture of hollow titanium blades for Axial design gas turbines.

Figure 5 shows two separate, already formed and consolidated parts 11, 15 Titanium or titanium alloy with integrated SiC fiber reinforcement. The fiber orientation and occupancy is adapted to the later operating conditions, the The fiber direction can be unidirectional or oriented several times. With blades the fibers run mainly in the direction of the centrifugal force, i.e. radial, with guide vanes other and multiple fiber orientations can be advantageous, for example, to counteract vibration forms in a targeted manner. The plate-shaped parts 11, 15 are curved to different degrees to form a hollow flow profile after the joining to build.

The reference symbol R with arrow indicates that the curvature is simplest Case can follow a circular arc line. Depending on the fluidic requirements but largely any spatial curvature curves can be realized. The parts 11 and 15 have metallic surfaces, which can be different Allow a cohesive connection, especially by welding and soldering. There are now solders and soldering processes for titanium and its alloys Allow connections that are equal in strength to the component material are.

In this sense, FIG. 6 shows a hollow airfoil 16 which is soldered out of the is added to both parts 11 and 15. The solder joints are in the area of the blade and the blade leading edge and are designated 17 and 18. A blade longitudinal axis, preferably the stack axis running through the center of gravity, is recognizable as a vertical arrow Z. In a gas turbine using the airfoil 16 The axis Z runs at least predominantly radially, starting from the Longitudinal central axis of the gas turbine, which can also be an aircraft engine. the It is clear to the person skilled in the art that the illustrated airfoil 16 is not yet ready for installation. Connection and functional elements are missing, e.g. a blade root with or without Platform, an inner and outer shroud segment in the case of a guide vane, a wear-resistant blade tip, etc. These elements consist entirely or partially made of a comparable metal, in particular a titanium alloy, and can contain ceramic fibers and / or particles. The item can be of different Alloys exist. which best suits local operating conditions are adjusted. Here, tomes like titanium fire resistance, wear resistance play etc. a role. The integral integration preferably also takes place by soldering.

This hollow bucket concept is of course also applicable to other, fiber-reinforced metals applicable, e.g. based on iron, nickel or cobalt (Fe, Ni, Co).

Claims (12)

1. A process for the fabrication of fibre-reinforced metal components with complex spatial geometry in which metal-coated SiC fibre sections - referred to here as SiC fibres - are bonded to each other and to the component metal by pressure imparted at high temperature in a vacuum and having the following process steps:

   A) metal-coated SiC fibres (4, 5, 6) in the desired quantity, distribution and orientation are applied to a metal sectional part (1, 2, 3) with simple geometry and held freely between the sectional part (1, 2, 3) and a metal counterpart (7, 8, 9), the counterpart (7, 8, 9) then being fixed to the sectional part (1, 2, 3),

   B) the unit (10) consisting of the sectional part (1, 2, 3), the fibres (4, 5, 6) and the counterpart (7, 8, 9) is formed plastically between form tools (12, 13) under pressure at high temperature in a vacuum until it achieves the desired complex geometry, no significant bonding together of the fibres (4, 5, 6) or bonding of the fibres to the metal of the sectional part (1, 2, 3) or the counterpart (7, 8, 9) yet having taken place at this point,

   C) the formed unit (10) is further compressed between the forming tools (12, 13) by increasing the pressure and/or the temperature and monolithically consolidated by means of metal bonding (diffusion welding) and the component (11, 15) fabricated in this manner is cooled and removed from the forming tools (12, 13) and where appropriate bonded to other components (11, 15), where appropriate also fabricated in the same manner
2. A process in accordance with claim 1,
   characterised in that
   titanium (Ti) and/or at least a titanium-based alloy is used as the coating metal for the SiC fibres and as the component metal.
3. A process in accordance with claim 1,
   characterised in that
   either nickel (Ni), cobalt (Co) or iron (Fe) and/or at least an alloy based on one of these elements is used as the coating, metal for the SiC fibres and as the component metal.
4. A process in accordance with one of claims 1 to 3,
   characterised in that
   a flat or simply curved section of a semi-finished product, for example a plate, a U-shaped section, etc., is used as the meta! sectional part (1, 2, 3 ).
5. A process in accordance with claim 2 or 4,
   characterised in that
   the plastic forming step takes place at a temperature of approximately 800°C and the consolidation step at a temperature of approximately 950°C.
6. A process in accordance with one or more of claims 1 to 5,
   characterised in that
   the counterpart (7, 8, 9) is fixed to the sectional part (1, 2, 3) by means of spot welding.
7. A process in accordance with one or more of claims 1 to 6,
   characterised in that
   several metal sectional parts (3) are positioned around the periphery of a wheel-shaped carrier (14) and oriented tangentially in terms of their planned fibre orientation,
   the sectional parts (3) are wound together with at least one long SiC fibre (6) by turning the carrier (14) until a predetermined number of fibres per component is achieved,
   a cover-like counterpart (9) is fixed to each sectional part (3) covering the fibre windings locally,
   the open fibre strands connecting the sectional parts (3) are separated and removed in the area of the ends of the sectional parts, and
   thus separated, the units which each consist of a sectional part, fibres and a counterpart (3, 6, 9) are removed from the carrier (14) and then plastically formed and consolidated in further steps.
8. A process in accordance with one or more of claims 1 to 7,
   characterised in that
   several units, each consisting of a sectional part, SiC fibres and a counterpart, are plastically formed together between forming tools, consolidated and where appropriate connected together by metal bonding, the units being positioned side-by-side/one behind the other and/or one on top of the other between the forming tools.
9. A process in accordance with one of claims 1 to 8,
   characterised in that
   at least two plastically formed and consolidated parts (11, 15) with identical or different geometry are bonded together to form a hollow component (16), in particular by soldering and/or welding.
10. A process in accordance with claim 9,
    characterised in that
    two consolidated, plate-shaped parts (11, 15), in particular parts having titanium (Ti) as the base metal, with different plate curvature are connected to form a hollow blade (16), in particular by means of soldering (17, 18).
11. A process in accordance with claim 10,
    characterised in that
    two plate-shaped parts (11, 15) curved in the shape of an arc of a circle at right angles to the subsequent longitudinal blade axis (Z) ― are connected.
12. A process in accordance with claim 10 or 11,
    characterised in that
    further parts such as a blade footing, a platform, one or two shroud segments or a blade tip, for example, are connected to the hollow blade (16), it being possible to use different alloys with special properties such as abrasion resistance, titanium fire resistance, fatigue resistance, etc. for the parts and the joining process required for the blade (16) and for the further parts (blade footing, etc.) may be carried out simultaneously or successively.

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