WO1990001472A1

WO1990001472A1 - Ceramic composite material, process for producing it and use thereof

Info

Publication number: WO1990001472A1
Application number: PCT/EP1989/000920
Authority: WO
Inventors: Nils Claussen; Nahum A. Travitzky
Original assignee: Nils Claussen
Priority date: 1988-08-05
Filing date: 1989-08-03
Publication date: 1990-02-22
Also published as: DE3837378A1

Abstract

A new ceramic composite material with appreciably improved strength values consists of a matrix of reaction-formed Si3N4 (RBSN) whose pores a filled with at least one element or one alloy chosen from the group Al, Si, Al alloy, Si alloy, Co- or Ni-based super-alloy, Ti alloy, intermetallic compound and transition alloy. It may also contain 5 to 40 vol.% of laminae, particles, whiskers and/or fibres. In addition, at least the pore-filling phase in the surface region may be converted to the corresponding nitride or oxide. The material is produced by treating the RBSN matrix with the liquid phase to be infiltrated under an inert gas at a pressure greater than 10 bar.

Description

Ceramic composite, process for its manufacture and use

The strength and fracture toughness of porous ceramics can be considerably improved in some cases by incorporating an elementary, in particular a metallic phase. Powder metallurgical or infiltration processes are most frequently used to produce such composite bodies (for example Kieffer and F. Benesovsky, "Hartmetalle", Springer-Verlag Vienna, 1965). Comparable metal-ceramic composites (e.g. MS Newkirk et al., "Formation of Lanxide Ceramic Composite Materials", J.Mater.Res.l (1986) 81 and EP-Al-0155831, 0169069, 0193292 and 0234704 ) getting produced. The infiltration of ceramics is usually simple when they are well wetted by the metals to be infiltrated and no undesirable reactions occur. This is the case with carbides, including WC and SiC (e.g. R. Kieffer et al. Ber.Det.Ker.Ges. 46 (1969) _. 486). DE-PS 1533312 describes, for example, the infiltration of carbides and nitrides of Zr, Hf, Nb, Ta, Cr, Mo and W with metals which react with the corresponding hard materials to form intermetallic compounds. Oxide ceramics present greater difficulties. However, Al 0 O-Al bodies have been successfully produced by pressure infiltration in the autoclave (G. Jangg et al., Ber.Dt. Ker. Ges. 48 (1971) 262).

Reaction-bound silicon nitride (RBSN), which always contains open pores due to its manufacturing process (see, for example, ME Washburn and WS Coblenz, "Reaction-Formed Ceramics", Am.Ceram.Soc.Bull. 67 (1988) 356), would be an interesting matrix for infiltration with reinforcing phases, especially AI and Si. To the - 1 -

Modifying the mechanical properties of RBSN, in particular increasing the fracture toughness, would be of interest to infiltrate RBSN with certain elements or alloys. Ceramics based on SiC (e.g. SiSiC) are known to be very successful.

Leimer and Gugel (Z. Metallkde. 66 (1975) 570) have described extensive attempts to infiltrate RBSN with a number of metallic alloys. The conclusion of these investigations was that no metals or non-metals could be found which could be infiltrated into RBSN without reaction. The substances examined were divided into 4 groups (see also BMFT final report NT 423, February 1976):

a) not wetting and not infiltrating b) well wetting but not infiltrating c) not infiltrating and reacting with Si, N and d) infiltrating and reacting with Si N.

Group d) only includes high-Ca deoxidation alloys with a high Ca content, for example CaSi and CaSi ₂ -Mg 10. The mechanical properties were compared, presumably due to the strong reactions of Ca with the Si _^ N. matrix the non-infiltrated RBSN hardly improved. These discouraging results were essentially confirmed by similar experiments by Schmidt (p. 447 in FL Riley (ed.), "Progress in Nitrogen Ceramics", M. Nijoff Publishers, The Hague, 1983). Here too, the unwanted calcium was required for infiltration, and reactions which had a negative effect on the properties also occurred. With very high pressures, such as are common in mercury porosimeters, RBSN might also be infiltrable with other metals or non-metals, but the technical effort would not be economically justifiable. According to a complicated, multi-stage process, porous Si, N. pressed or sintered bodies were infiltrated with a Mg-containing Al alloy at a pressure of 2000 bar (DE-OS 24 02 872, 24 13 977.3-24, 24 06 601).

Under the impression of this knowledge and failures, apparently no further attempts to infiltrate RBSN with unreacted metals and non-metals were carried out.

The object of the invention is to improve the physical properties of RBSN by incorporating a phase which does not react with the matrix and to create a process which enables the production of composite ceramics of this type in a simple and economical process.

This object is achieved according to the invention by a ceramic composite body, which is characterized in that it consists of a matrix of reaction-bonded Si, N. (RBSN), the pores of which are filled with at least one element or an alloy selected from the group Al, Si, Al alloy, Si alloy, superalloy based on Co or Ni, Ti alloy, intermetallic compound and Transition alloy.

The pores are preferably filled with Al or Si, or an Al or Si alloy. The invention is based on the surprising finding that a complete infiltration of an RBSN body takes place at 40 bar in melt reaction tests with an Mg alloy containing Si and Si alloy in a pressure sintering furnace. Furthermore, it was found that under an inert gas atmosphere, significantly lower pressures were sufficient for infiltration with RBSN even with very fine pore distribution. It was found that the infiltration under these conditions is obtained not only with aluminum alloys containing magnesium and / or silicon, but also with pure, unalloyed aluminum and with pure silicon and with aluminum or / and magnesium alloyed silicon, and also with the other pore-filling elements and alloys according to the invention.

The metal phase of the composite body according to the invention preferably consists of pure aluminum or aluminum with a content of 0.5 to 15% by weight of Si and / or Mg.

In a further preferred embodiment, the phase present in addition to the Si-.N ₄ consists of pure Si or a Si alloy with 1 to 10% by weight of Al and / or Mg.

In addition, the composite body according to the invention can also contain reinforcing elements in the form of platelets, particles, whiskers or fibers made of SiC or / and Al ^ O-. This further improves the mechanical properties.

According to a further preferred embodiment of the invention, the phase lying in the surface area, for example in particular the Al or Si phase, is at least partially in the corresponding nitride, for example in A1N or Si_N. or converted into an oxide. In this way, a sealing of the phases lying inside the body and a further increased surface hardness can be achieved. The surface compressive stresses occurring during this conversion also contribute to the improvement in strength.

The process according to the invention for producing the ceramic composite body is essentially characterized in that the matrix consisting of RBSN is treated with the liquid phase to be infiltrated under an inert gas at a pressure of more than 10 bar. If aluminum or an alloy of aluminum with Si or / and Mg is used as the liquid phase, temperatures between 700 and 1300 ° C., preferably between 775 and 875 ° C., are expediently used. Pressures between 20 and 100 bar are preferably used, particularly preferably between 30 and 60 bar. Pressures above 100 bar can also be used, but despite the increased outlay they do not result in better products than those obtained in the pressure ranges preferred according to the invention. Argon is preferred as the noble gas, but helium or krypton and xenon can also be used.

If the matrix is infiltrated with silicon, the same pressures as for aluminum and aluminum alloys and temperatures between 1470 and 1800 ° C., preferably between 1500 and 1650 ° C., are expediently used. In the other phases, the pressure ranges are expediently the same as for Al or Si.

If surface sealing by reaction of the infiltrated phase with a reactive substance applied to the surface is desired, can this is done simply by replacing the noble gas phase used for the infiltration with nitrogen. The nitrogen can be used under the same pressure at which the infiltration took place, for example by gradually replacing the noble gas with nitrogen while maintaining the pressure. However, nitridation with nitrogen can also be carried out at lower pressures down to 1 bar.

Instead of nitrogen, other substances which react with the infiltrated phase to form corresponding hard ceramic phases can also be used for the surface sealing. For example, an infiltrated phase made of Si with a medium containing carbon or boron can be superficially converted into SiC or SiB.

Surface sealing can also be achieved by oxidation of the infiltrated phase, especially in the case of Al. For this purpose, the infiltrated RBSN body is appropriately oxidized by annealing in an oxygen-containing atmosphere such as air at 600 to 1200 ° C. under normal pressure.

When infiltrating an RBSN matrix with a density of approx. 2.6 g / cm, it is often sufficient to embed the matrix in Si or Al powder, for example, or to cover it with solid Si or Al and then melt it. In the case of more porous RBSN, care must be taken to ensure that the specifically lighter matrix body does not float in the liquid phase. This can be done by means of mechanical devices, for example made of a ceramic such as Al 0 _3, or by inserting heavy elements or compounds which increase the density of the RBSN over that of the liquid phase. Particularly easy is to prevent the RBSN body by retaining pins, for example of Al _j O. ,, from floating on the liquid phase, such as the Si or Al melt.

In the case of surface sealing by reaction with nitrogen, the depth of the nitrided edge zone depends on the nitrogen pressure and the nitrogen exposure. For example, with a nitrogen pressure of 40 bar and an exposure time of one hour at 825 ° C, a nitrided layer of the same thickness as that of a nitrogen pressure of 1 bar and a holding time of 24 hours at 1200 ° C was achieved. At high nitrogen pressures of about 80 bar or more, AlN was even found inside the RBSN samples infiltrated with Al phase. It is assumed that this is brought about by precipitation from a nitrogen-supersaturated Al melt. Sufficiently long nitridation makes it possible to convert the infiltrated phase largely or completely into the corresponding nitride and thus e.g. to create a dense Si, N. body.

Practically all known types of RBSN can be used as matrix material. This includes both commercially available products and matrix bodies produced and subsequently nitrided by nitriding compressed Si powder, which may also contain reinforcing elements. The production of such RBSN bodies is known to the person skilled in the art and requires no further explanation here.

The production of the composite body according to the invention does not require any special equipment. It can be done in a conventional pressure sintering furnace. An expedient embodiment of the method according to the invention for producing the ceramic composite body consists in immersing the RBSN matrix body in the liquid phase to be infiltrated with the aid of a dipping device provided with passages for the liquid phase, then applying the noble gas pressure and then the immersion device is removed from the liquid phase and allowed to drain. This dipping device is provided with openings through which the melt can flow in and out; It preferably consists of a cylinder or a prism which is open at the top, preferably with a square base, the base and side surfaces being provided with corresponding openings and formed, for example, as a sieve. After the infiltration, the dipping device with the RBSN body is then removed from the melt, the excess liquid phase being able to drip off.

The invention therefore also relates to a dipping device for carrying out the method for producing the ceramic composite body according to the invention, consisting of a container with passages for the melt to be infiltrated, an insertion opening for the RBSN matrix body, a holding device for the matrix body and with a suitable holding device for inserting and removing the immersion device from the melt of the phase to be infiltrated.

The container expediently has the shape of a cylinder which is open at the top or a prism with a preferably square base area, the base area and the side areas having correspondingly large passage openings for the melt and being designed, for example, as a sieve. The material of the diving device is selected so that it is suitable for the infiltration alloy used in each case.

1 shows an embodiment of a device according to dive during erfindungs¬ (Figure la) and after insertion (figure ^"lb) in the melt.

In this embodiment, the RBSN sample (1) is located in the container (4), which is preferably a cylindrical AI, 0 -.- crucible, which is provided with openings (5); the RBSN sample (1) is fastened in the container by a suitable holding device, for example a vertical (8) and / or horizontal (9) holding rod; A holding device (6), for example a metal wire, is attached to the container (immersion device), by means of which the immersion device can be introduced and removed from the Al _^ C crucible (3) in which the melt (2) is located. The Al 0 -.- crucible (3) is located between graphite heating elements (7) of a conventional pressure sintering furnace.

By sealing the surface of the infiltrated RBSN of the invention, in particular, for example, with AlN or Si_N. , the wear resistance of the body is increased and melting or evaporation of the phase, for example the Al or Si phase, is prevented from the pores when used at temperatures above the respective melting points of these phases. The infiltration method according to the invention is particularly suitable for RBSN ceramics reinforced with particles, fibers and platelets. Due to the characteristic porosity of the RBSN, such composites have only moderately improved properties compared to the pure RBSN. For example, an RBSN body containing randomly distributed SiC platelets (American Matrix Inc., Knoxville, TN / USA, diameter <100 μm) was completely infiltrated with Si. Such a composite body, which additionally " sealed 'was an _{exceptionally} high Ver¬ showed less wear. It can be used as a cutting ceramic insert for very high feed rate.

The following can be mentioned as advantages of the RBSN infiltrated according to the invention over non-infiltrated RBSN:

1. Significant improvement in fracture toughness (from 2.5 to> 4.2 MPa </ m) and strength (from * approx. 250 to ^ 400 MPa). RBSN qualities with higher initial strength can be improved accordingly.

2. The temperature shock resistance is considerably increased, firstly because of the increased fracture toughness and secondly because of the improved thermal conductivity. For example, the thermal resistance parameter used to assess the TWB behavior of ceramics is R ¹ in infiltrated RBSN

30 kW / m and only 3.9 kW / m for non-infiltrated RBSN.

3. The material can be machined by electrical discharge, which represents a considerable technological advantage for the production of precision parts. Pure RBSN cannot be processed by electrical discharge machining because the electrical conductivity is insufficient.

4. The sealing by a later annealing in leads to significantly better wear properties (approx. 5 x better) and prevents melting or evaporation at application temperatures> ^Λ * '600 ° C (AI) or at T> - »1400 ° C (Si). - if -

5. RBSN, which contains platelets, whiskers or fibers, is particularly enhanced in its mechanical properties by infiltration.

6. The metal-containing RBSN body can be easily connected to metallic components (e.g. also by soldering).

7. RBSN, which was initially infiltrated with Si and then nitrided for a long time under pressure, is suitable as a creep- and high-temperature-resistant construction element due to the lack of second phases (apart from any residual silicon).

8.Silcated infiltrated RBSN (in particular with Si or Al) is a toxicologically harmless material for metal-cutting tools (e.g. indexable inserts) for metalworking due to its high wear resistance and good thermal conductivity.

9.Sealed, infiltrated RBSN is a shock-absorbing, very light material due to its improved fracture toughness and the permanent compressive stresses introduced by sealing. In combination with an easily solderable backplate made of AI, it is used as a light armor element e.g. can be used to ward off projectiles.

On the basis of the properties explained in more detail above, the composite bodies according to the invention are particularly suitable as indexable inserts for machining metals, as wear-resistant components in engine, machine and apparatus construction, as material (preform) for spark-erosive machining of precision parts and as a metallizable element for connections (eg soldered connections) with metal parts and as a light armored element, eg in connection with a back plate made of aluminum.

For use as a metallizable element for connections with metal parts, that is to say for the production of a firm connection between the infiltrated RBSN part (composite body) and a metallic support construction, the procedure is preferably such that the metal / composite body (ceramic) connection point metal melt used when infiltrating the RBSN part is maintained as a layer and the metallic part is then replaced by any conventional connection technology, for example by soldering, welding, etc., connects. In an expedient embodiment, the metal layer which is connected to the pore structure in the composite body (RBSN body) itself acts as a support structure.

FIGS. 2a and 2b show some embodiments of the connection possibilities (joining) of RBSN parts (21) according to the invention with a metallic support (22). The metallic support (22) can in turn be soldered onto a metallic part (23) (Figure 2c) or shrunk into one (Figure 2d). The following examples illustrate the invention widely

The experiments for infiltration with Al were carried out in an A1_0, crucible, in which a cylindrical RBSN plate was covered by an Al disk which fit straight into the crucible. After reaching the melting temperature of the AI (• * - ^■■ 700 ° C), the RBSN plate was obviously wetted on all sides by the AI, ie it did not float on the liquid AI melt, which would have been expected due to the density ratio : AI has a specific density of almost 2.7 g / c while the RBSN samples used were slightly light (2.4 to 2.6 g / cm ³ ). The following method was used for infiltration with Si: Si powder was pressed isostatically onto the RBSN cylinder. After reaching the melting temperature of the Si (• * ^** • ^• • ^■ 1500 ° C), the liquid Si completely enveloped the RBSN sample. The industrially simplest and safest method is a mechanical fixing of the RBSN parts in the crucible, spielsweise by top patch Al _o 0 -, - pens,

** • * "^ that buoyancy would be prevented in any case.

In Examples 1 to 12 described below, each was heated in vacuo to the melting temperature of Al or Si and an argon pressure between 5 and 80 bar was applied. The respective argon pressure was maintained until it cooled to the solidification temperature in order to prevent the metallic phase from exuding from the RBSN body. However, glow tests in nitrogen at lower pressures show that the infiltrated phase can also be cooled at pressures below the infiltrating pressure, because even at 1 bar N at 1000 ° C., infiltrated AI no longer escaped from the RBSN body. However, an AIN de-layer was present in this case. All samples of the following example - m -

were X-rayed and examined with EDAX. No connections or reactions were found.

Example

Commercial, reaction-bound silicon nitride (RBSN) (Annawerk) with a specific density of 2.59 g / cm ³ and a pore distribution with a maximum frequency of 0.1 μm and a measured open porosity of 17.9% was in the form of a disk 15 mm in diameter and 6 mm in height placed in a cylindrical crucible made of A1_0_ and with an aluminum alloy (2.5% by weight of Mg, 5% by weight of Si and 1% by weight of Zn) also in the form of a disc covered. This system was then heated in a pressure sintering oven under vacuum at a heating rate of 15 ° C./min from room temperature to 825 ° C. and held at this temperature for 50 minutes. An argon pressure of 40 bar was then applied within 15 minutes and held for 15 minutes. The mixture was then cooled at 15 ° C./min to 550 ° C. at constant pressure, the pressure was then released and the sample was cooled to room temperature by switching off the oven.

After this treatment, even the finest pores visible in the scanning electron microscope were completely infiltrated with Al.

The fracture toughness, measured by the ICL method, was 4.2 MPa m. The RBSN used without AI has a fracture toughness of 2.7 MPa * / m.

The same tests were also carried out at 5, 20, 60 and 80 bar (see also Table 1). "\ ζ -

Example: 2

As described in Example 1, the RBSN from Example 1 was infiltrated with technically pure Al (99.9%) at 30 and 80 bar instead of with the Al alloy. The pores were then completely filled with AI.

Example 3

Commercial RBSN (Hoechst CeramTec) with a specific density of 2.50 g / cm ³ and a sintering aid additive of ^<~~ * 5% by weight A1-0- and 5% by weight Y ^ O-, was, as described in Example 1, heated together with the aluminum alloy in a vacuum to 775 ° C; after reaching this temperature, an Ar pressure of 80 bar was applied in vacuo within 15 minutes without a holding time. After reaching 80 bar, that is to say after 15 minutes, the pressure was cooled to 550 ° C. while maintaining the pressure, as in Example 1, then the pressure was reduced to atmospheric pressure and the system was cooled to room temperature.

As in Example 1, the RBSN sample was completely infiltrated with Al.

Example 4

RBSN from a test series (Iscar) with a specific density of 2.48 g / cm ³ was, as described in Example 2, with an Al alloy (2.5 wt.% Mg, 5 wt.% Si and 1% by weight of Zn) infiltrated at an Ar pressure of 20 bar. Larger pores down to 0.1 μm were then infiltrated, while pores below 0.1 μm were still open. When using pure AI - -

(99.9%) under otherwise identical infiltration conditions, the diameter of the not yet infiltrated pores shifted to somewhat larger values (0.2 μm). Complete infiltration was obtained at infiltration pressures of 30 and 60 bar.

Example 5

As in Example 1, the RBSN qualities used in Examples 1, 3 and 4 were subjected to an Ar pressure of 5 bar. Infiltration was then found neither with Al nor with an Al alloy (see Example 3).

Example 6

As described in Example 1, the RBSN from Example 1 was covered with an Al disk (99.9% Al), the amount of which, after the pressure infiltration, just filled the lateral space around the sample, including the pores in the sample . After an infiltration time of 15 minutes at an Ar pressure of 40 bar, the Ar pressure was continuously reduced to 0 within 15 minutes, while a nitrogen (N_) -

Second

Pressure was built up in such a way that the sum of the partial Ar and N ₂ pressures was constant at 40 bar. The N pressure of 40 bar was kept at 825 ° C for 1 hour, after which it was cooled as described in Example 1.

After this treatment, the sample completely infiltrated with Al contained an AlN layer on the upper side that only protrudes from the Al bath and is only thinly wetted with Al Pore channels reached into it. The transition area consisted of a cermet-like structure made of Al and AlN.

Example 7

As described in Example 2, the RBSN of Example 1 was infiltrated only with an Ar pressure of 40 bar and pure Al. The completely infiltrated sample was ground and thus the supernatant AI was removed. The sample treated in this way was then reduced to 500 ° C. at 25 ° C./minute and then at 0.5 ° C./minute to 1200 ° C. under 1 bar heated up and held there for 24 hours. After furnace cooling (> 15 ° C./minute) to room temperature, an AIN seal similar to that of the sample from Example 5 was found. A "sweating" of the liquid AI suspected in this way of working did not occur.

In an abrasive wear test on 600 mesh SiC paper (1 m path length at a surface pressure of 1000 bar), the sample sealed in this way was 5 times more wear-resistant than the corresponding untreated RBSN sample.

Example 8

The RBSN of Example 1 was packed in the form of a cylindrical disk in pure silicon powder (Si: 99.99%) in a rubber mold. The Si powder was then pressed onto the disk at an isostatic pressure of 500 bar. This system was heated in an A1 "0 -.- crucible at 15 ° C / minute in vacuo in a pressure sintering oven to 1575 ° C. Then there was an Ar print - Ifi -

of 80 bar within 30 minutes and held for 15 minutes. The mixture was then cooled to 1350 ° C. at constant Ar pressure (80 bar) and, after this temperature had been reached, the pressure was cooled to normal pressure and the temperature to> 15 ° C./minute to room temperature.

After this treatment, the sample was infiltrated with Si similarly to the sample from Example 1. Uninfiltrated open pores could not be found in the SEM. The ISB fracture toughness was 4.1 MPa / ϊή and the wear resistance was improved many times over untreated R3SN. The hardness (HV, 100 X) was 1530 GPa compared to only 510 for non-infiltrated RBSN.

Example: 9

RBSN was treated as described in Example 8 at pressures of 5, 20 and 30 bar. The samples were not infiltrated at 5 bar and only partially infiltrated at 20 bar. Only a pressure of 30 bar led to complete infiltration.

Example 10

The RBSN from Example 1 was completely infiltrated with Si, as described in Example 8, but at a pressure of 40 bar. After grinding, the sample was nitrided in the same pressure sintering furnace at 40 bar “on the surface at 1575 ° C. for 2 hours. The sample then consisted entirely of Si 3-, N4 ,, in the surface area, while also in the inner Si channels Si 3_N4, -ausscheidunσen im - I ₅ -

Transmission electron microscope (TEM) could be seen.

An annealing treatment of a sample sealed in this way at normal pressure (1 bar) in air at 1500 ° C. did not lead to melting out of the Si phase which was liquid at this temperature.

Example: 11

Silicon powder (average diameter 5 μm) was mixed with 20 vol.% Silicon carbide platelets ( ^~ K -SiC platelets, <100 μm diameter, approx. 5 μm thick, from American Matrix Inc.), isostatically into rods at 2000 bar (3 x 3 x 30 mm) and then nitrided at 1420 ° C in a pressure and atmosphere controlled oven for 10 hours to form an RBSN matrix reinforced with SiC platelets. The bodies thus obtained were then, as described in Example 9, infiltrated with Si and surface-sealed. In an abrasive test on 600 mesh SiC paper, which led to severe surface damage with pure RBSN, no measurable wear was found. The ICL fracture toughness was 7.5 MPaVln.

Example 12

The RBSN infiltrated according to Example 1 was annealed for 24 hours at normal pressure (1 bar) in air at 1150 ° C., heating to this temperature at 10 ° C./minute. There was no "exudation" (due to the Al ^ O sealing). - 10 ^~

The following table shows the strength, fracture toughness and hardness values for Examples 1, 3 and 4.

TABLE 1

RBSN- infiltration strength fracture toughness, MPav / m hardness matrix infiltrated pressure MPa ISB 2) ICL3) HV 10 (100 N) phase bar

according to not infiltrated 227 - 15 2.7 - 0.15 510 Example Al alloy 5 230 - 17 2.6 - 0.2 520 1 20 320 12 3.5 i 0.2 3.96 - 0.14 1000 60 463 - 15 3.9 ~ 0.1 4.79 - 0.11 1150 80 450 - 18 4.52 ⁺ 0, ll 5.23 - 0.15 1170

AI (99.9%) 80 478 - 15 5.0 - 0.2 5.58 - 0.14 1100 Si (99.99%) 80 427 - 20 3.9 - 0.2 4.74 - 0. 11 1530

according to not infiltrated not measured 550 Example Al alloy 80 not measured 5.0 - 0.08 1340

3 according to not infiltrated not measured 216 Example Al alloy 60 not measured 4.15 - 0.1 900

4 Si (99.99%) 80 not measured 3.6 0.2 960

1) 2.5% by weight of Mg, 5% by weight of Si and 1% by weight of Zn, balance AI 2) Indentation-Strength in Bending (3-point test)

- 11 -

Example: 13

The RBSN from Example 1 was infiltrated as described in Example 1 with the metal alloys listed in Table 2 at a temperature of 1575 ° C. for 5 min at a pressure of 80 bar. In order to prevent floating on the melt, the cylindrical RBSN samples were clamped to the bottom of the Al 0 -.- crucible. Before melting, the metal alloy lay as a cylindrical disc on the RBSN sample.

In all cases, the pores were completely filled without a measurable reaction (actually expected) between RBSN and the alloy.

TABLE 2

No alloy

1 Ti + 39 wt .-% AI

2 Ti - 6 AI - 4 V

3 Maraging steel 18 Ni (250)

4 Inconel 601 (60.5 Ni - 23 Cr - 14.1 Fe - 0.5 Cu - 1.35 AI - 0.05 C - 0.5 Mn

5 Co Alloy 21 (Co - 27 Cr - 5 Mo - 2.8 Ni - 0.2 C)

The mechanical properties of the alloy # 1 infiltrated RBSN were:

4-point bending strength: 510 MPa; K (ICL): 4.9 + 0.5 MPa Tm; Hardness HV 10: 15.24 GPa. - ^ -

Example 14

In order to avoid removal (grinding, etc.) of the solidified metal melt from the RBSN samples, a simple immersion device according to FIG. 1 was used, with the aid of which the infiltrated samples were pulled out of the liquid metal bath. A large part of the melt dripped off the sample. The sieve-like immersion device consisted of an Al-0 -.- crucible perforated with large holes. As described in Example 2, the experiment was carried out with pure AI in the manner of Example 1.

Example 15

A cylindrical RBSN sample (RBSN as in Example 3) with a diameter of 15 mm and a height of 8 mm was firmly inserted in an Al »0 -.- crucible with a 15 mm inner diameter and with a 15 mm wide ^" . And 5 mm high disc made of pure Al, followed by the same procedure as in Example 3, except that the holding time was only 5 min at 775 ° C. After the cycle was completed, the infiltrated RBSN sample had an Al layer (22 ) of about 3 mm in thickness, as shown in Figure 2b It is obvious that this layer can serve not only as a connecting layer, but also itself as a functional part (eg (33) in Figure 2c).

Claims

Patent claims

1. Ceramic composite body, so that it consists of a matrix of reaction-bonded Si-.N. (RBSN), whose pores are filled with at least one element or an alloy selected from the group Al, Si, Al alloy, Si alloy, superalloy based on Co or Ni, Ti alloy, intermetallic compound and transition alloy.

2. Composite body according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the pores are filled with an Al alloy containing 0.5 to 15 wt .-% Si and / or Mg or / and Zn.

Composite body according to claim 1 or 2, so that it additionally contains 5 to 40% by volume of platelets, particles, whiskers and / or fibers.

4. Composite body according to claim 3, d a d u r c h g e k e n n z e i c h n e t that the platelets, particles, whiskers and / or fibers consist of SiC and / or A1_0_.

5. Composite body according to one of the preceding claims, characterized in that at least the pore-filling phase lying in the surface area is converted into the corresponding nitride or oxide and exerts breaking stresses.

6. A method for producing a composite body according to any one of claims 1 to 5, that the matrix consisting of RBSN is treated with the liquid phase to be infiltrated under an inert gas pressure of more than 10 bar.

7. The method according to claim 6, characterized in that the RBSN matrix body is immersed with the aid of a dipping device provided with passages for the liquid phase in the liquid phase to be infiltrated, then applies the inert gas pressure and then the dipping device is again removed from the liquid phase and dripped leaves.

8. The method according to claim 6 or 7, characterized in that the pores of the matrix by contacting with pure or 0.5 to 15 wt .-% Si or / and Mg and / and Zn containing aluminum at a temperature between 700 and 1300 ° C. be filled under an inert gas pressure of more than 10 bar.

9. The method according to claim 8, d a d u r c h g e k e n n z e i c h n e t that a temperature of 775 to 875 ° C is applied.

10. The method according to claim 6 or 7, characterized in that the pores of the matrix are filled by contacting with pure Si at a temperature between 1470 and 1800 ° C under an inert gas pressure of more than 10 bar. -lέ-

11. The method according to claim 10, d a d u r c h g e k e n n z e i c h n e t that a temperature of 1500 to 1650 ° C is applied.

12. The method according to any one of claims 6 and 8 to 11, so that the matrix is packed in a powder bed from the phase to be infiltrated, then evacuated in the pressure sintering oven, heated and then the inert gas pressure is applied.

13. The method of claim 12, d a d u r c h g e k e n n z e i c h n e t that the matrix is packed in a powder bed made of Al or Si and heated in the case of Al to temperatures between 700 and 1300 ° C and in the case of Si to temperatures between 1500 and 1800 ° C.

14. The method according to any one of claims 6 to 13, so that a noble gas pressure of 20 to 100 bar is applied.

15. The method according to claim 14, d a d u r c h g e k e n n z e i c h n e t that an inert gas pressure of 30 to 60 bar is applied.

16. The method according to any one of claims 12 to 15, characterized in that an RBSN matrix is used in which a heavy element or a compound thereof is dispersed in such an amount that the density - -

the matrix is larger than that of liquid Si or Al.

17. The method according to any one of claims 13 to 16, d a d u r c h g e k e n n z e i c h n e t that the matrix by fastening body from A1_0-. presses under the surface of the Si melt.

18. A method for producing a composite body according to claim 5, according to one of claims 6 to 17, characterized in that the nitridation is carried out at the pressures and temperatures which are used in the infiltration of the matrix and the noble gas gradually by maintaining the total pressure constant Nitrogen replaced.

19. The method according to claim 18, d a d u r c h g e k e n n z e i c h n e t that nitriding at N _ "_- pressures of 1 to 5 bar.

20. A method for producing a composite body ge according to claim 5, according to one of claims 6 to 17, characterized in that in Al-infiltrated RBSN by annealing in air at temperatures between 600 and 1200 ° C at normal pressure, the surface by oxidation and thereby generated surface compressive stress is sealed.

21. The method according to any one of claims 6 to 20, characterized in that argon is used as the noble gas. -IS-

22. Dipping device for carrying out the method for producing a ceramic composite body according to one of claims 1 to 5, consisting of a container (4) with passages (5) for the melt to be infiltrated (2), an insertion opening for the RBSN matrix body (1 ), a holding device (8, 9) for the matrix body and with a device (6) for introducing and removing the device from the melt of the phase to be infiltrated.

23. Diving device according to claim 22, so that the container (4) has the shape of an open-top cylinder or a crucible, the base and side surfaces of which are provided with openings.

24. Diving device according to claim 22 or 23, so that the base and side surfaces of the container consist of a grid.

25. Use of a composite body according to one of claims 1 to 5 as an indexable insert for machining metals, as a wear-resistant component in engine, apparatus and machine construction or as a material for spark-erosive machining of precision parts.

26. Use of a composite body according to one of claims 1 to 5 as a light armor element in connection with a back plate made of aluminum. -23-

27. Use of a composite body according to one of claims 1 to 5 as a metallizable element for connections with metal parts.

28. Use according to claim 27 for producing a firm connection between the composite body and a metallic support structure, characterized in that the metal melt used in infiltrating the RBSN part is maintained as a layer at the metal / composite body connection point and the metallic part then connects to this layer using a conventional joining technique.

29. Use according to claim 28, so that the metal layer which is connected to the pore structure in the composite body itself functions as a support structure.