Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C47/00—Making alloys containing metallic or non-metallic fibres or filaments
  • C22C47/02—Pretreatment of the fibres or filaments
  • C22C47/025—Aligning or orienting the fibres
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C47/00—Making alloys containing metallic or non-metallic fibres or filaments
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C47/00—Making alloys containing metallic or non-metallic fibres or filaments
  • C22C47/14—Making alloys containing metallic or non-metallic fibres or filaments by powder metallurgy, i.e. by processing mixtures of metal powder and fibres or filaments
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C49/00—Alloys containing metallic or non-metallic fibres or filaments
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C49/00—Alloys containing metallic or non-metallic fibres or filaments
  • C22C49/02—Alloys containing metallic or non-metallic fibres or filaments characterised by the matrix material
  • C22C49/08—Iron group metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy

Definitions

• the present invention relates to a high tenacity composite material comprising a binder matrix and a fibrous reinforcing phase, as well as to a process for the manufacture of such a composite material.
• K IC are of the order of 3 to 5 MPa m1 ⁇ 2 for monolithic ceramics, such as Al2O3, SiC, Si3N4, for the compounds Al2O3 + TiC and Sialons, while the values of r are between 200 and 700 MPa.
• these are ceramic materials reinforced with fibers, for example graphite fibers, which have a stress intensity factor and a very high tenacity at low temperatures; on the other hand, at high temperatures, their performance is poor, because on the one hand there is an oxidation of the carbon fibers and on the other hand a reaction between the carbon of the fibers and the ceramic matrix.
• fibers for example graphite fibers, which have a stress intensity factor and a very high tenacity at low temperatures
• fibers for example graphite fibers, which have a stress intensity factor and a very high tenacity at low temperatures
• fibers for example graphite fibers, which have a stress intensity factor and a very high tenacity at low temperatures
• These fibers have a polycrystalline structure which recrystallizes at high temperature and makes the use of such materials delicate at these temperatures, because they become brittle by reducing the reinforcing characteristics of the fibers. These materials are therefore ill-suited to shaping by hot isostatic pressing in particular.
• composite materials implicitly associates the idea of reinforcing a material constituting the matrix of low mechanical strength by very strong and very rigid fibers. This effect is all the more important that the Young's modulus of the fibers is large compared to that of the matrix and that the volume fraction of the reinforcement is high; but at constant volume, the reinforcing effect is greater for fibers with very high elastic modulus.
• the strain at break of the matrix must be greater than that of the fiber and the fiber-matrix adhesion must be good so that there is no reduction in the mechanical properties by default of matrix-fiber adhesion.
• Several solutions have been proposed, including hot pressing or hot isostatic repressing. However, all of these solutions prove to be insufficient in certain cases, in particular when the impact resistance must be high.
• the object of this invention therefore consists in remedying the abovementioned drawbacks and in providing a composite material which, in addition to resistance to high temperatures, has a high tenacity and is very chemically stable.
• the composite material which is the subject of the invention and which aims to achieve the above object has the characteristics defined in claim 1.
• Another object of the present invention consists of a process for the production of this composite material, which is as defined in claim 8.
• the fact that the ceramic reinforcing fibers, embedded in the binder matrix, are previously "encapsulated" in a thin refractory sheath, makes it possible to obtain excellent wettability of the fibers in the matrix, without destruction of the refractory layer during sintering.
• the composite material thus obtained therefore has a high tenacity, and is practically free from cracks, the fiber itself contributing to the tensile strength, while the refractory sheath and the binding phase lead to obtaining good compression strength.
• the matrix or binding phase can be constituted by a metal, such as Fe, Ni or Co, by an alloy of these or another metallic alloy, optionally with a transition metal carbide.
• this binding phase may contain additional elements or compounds intended to improve the wettability of this metallic binding phase.
• additional elements or compounds are, for example, a metal from the Pt group, such as Ru, Os, Ir, Rh, Pd and Pt, Ru being preferred, or Re, or alternatively transition metal carbides such as carbides of Ti, W, V and Mo.
• These additional elements or compounds should in principle not be present in an amount greater than about 20% by weight of the binding phase; preferably they represent from 5 to 20% of this binding phase.
• the choice of the binding phase must be made taking into account that it must wet the protective coating of the fibers and not dissolve it.
• the fibrous phase generally represents from 5 to 40% volume of the composite material, preferably from 15 to 25% vol. Above 40%, it is difficult to remove all the sintering porosities, even by hot isostatic pressing, while below 5% the reinforcing effect is too weak.
• the ceramic fibers constituting it have a diameter of between approximately 0.5 to 5 microns. The length of these fibers can vary, from a few microns for short fibers or "whiskers" to a few mm for long fibers, more particularly from 0.01 to 10 mm.
• fibers in the present invention those consisting of simple elements such as W, B and C, or else carbides, nitrides, borides, carbonitrides, oxides, etc. transition elements, such as Al2O3, SiO2, BeO, ZrO2, B4C, SiC, WC, Si3N4, BN, AlN, etc.
• one of the important characteristics in the present invention consists in rendering the matrix or binding phase non-reactive with the fibers, by first coating the latter with a protective deposit, the thickness of which is generally of the order of 1 / 10 of the diameter of the fibers coated by said deposit.
• This deposit therefore has the role of preventing a chemical reaction at the interface between the matrix and the fibers during sintering in the liquid phase or use at high temperature.
• the thin protective coating consists for example of C, of B, of a carbide, nitride, boride, carbonitride and oxide of transition metals, such as B4C, TiC, SiC, W2C, WC, HfC, BN, TiN, Si3N4 , HfN, TiB2 Al2 O3 and TiAlON.
• transition metals such as B4C, TiC, SiC, W2C, WC, HfC, BN, TiN, Si3N4 , HfN, TiB2 Al2 O3 and TiAlON.
• the coating of the fibers can be carried out using any known technique in the gas, liquid or solid phase.
• the deposition by gas chemical or physical
• the following layers can be obtained by CVD, using as the gaseous reagent that indicated in parentheses: C (CH4C3H8); B (BCl3-H2); B4C (BCl3-CH4-H2); BN (BF3-NH3 / BCl3-NH3); TiC (TiCl4-CH4-H2); TiN (TiCl4-N2-H2); Si3N4 SiCl4-NH3); Al2O3 (AlCl3-CO2-H2); SiC (CH3SiCl3-N2) and TiB2 (TiCl4-BCl4-H2)
• TiC TiC-Ni
• TiN TiC-Ti-N2
• W2C W2C-W
• WC WC-W
• HfN HfN-Hf-N2
• HfC HfC-Hf
• TiAlON Al2O3-TiN
• the choice of coating material obviously depends on the two binding and fibrous phases respectively present, with the aim of protecting the fibers by preventing their reaction with the binding phase during sintering or use at high temperature.
• the coating at the interface of the two phases must be put in compression, that is to say that the expansion coefficient of the protective coating must be less than or equal to that of the matrix and the fibers, at temperature ambient.
• the binder phase can be provided so that it reacts with the protective coating, however without dissolving the latter, for example by dissolution-precipitation reaction; in this case, the binding phase must for example be saturated with the element or the compound constituting the protective coating.
• the manufacturing of composite material according to the invention firstly comprises mixing the metallic binder phase, in powder form, with the fibrous phase formed from fibers previously covered with the protective layer, this mixture generally being carried out in a liquid medium.
• the shaping of the material obtained is carried out by any technique of powder metallurgy, for example by pressing, by extrusion, by injection, by casting, etc. It may be important, during the shaping step, to orient the fibers, in particular to obtain articles intended to be subjected to particularly high stresses at high temperature.
• the shaping techniques to be used are those by injection, by extrusion or by formation of flexible film.
• a sintering is carried out, by conventional treatment (pre-sintering-sintering) followed or not by hot repressing, or else directly by hot isostatic pressing.
• a slip is first prepared by mixing the metallic binder phase, in powder form, with an organic product in the liquid state, for example paraffin or a mixture of paraffins, polyethylene glycol, oil. castor oil, etc., or a mixture thereof, for example paraffin and polyethylene glycol.
• an organic product in the liquid state for example paraffin or a mixture of paraffins, polyethylene glycol, oil. castor oil, etc., or a mixture thereof, for example paraffin and polyethylene glycol.
• the fibers can be added at two stages: if they are short fibers, they can be mixed during the grinding of the slip, in order to obtain a homogeneous distribution and eliminate the risk of agglomeration of said fibers; if it is about long fibers, they can be incorporated after degassing of the slip, or, in the case of a sheet of fibers, be impregnated with the slip to make shaped articles.
• the composite material has been shaped as mentioned above, possibly with a particular orientation of the fibers,: 1 is subjected to sintering, at a temperature of between 300 and 700 ° C., which leads in particular to the decomposition and the volatilization of the liquid organic support used to prepare the slip.
• Sintering is carried out under vacuum or in the presence of an inert gas, the type of gas depending in particular on the nature of the fibers and of the matrix.
• the composite material according to the invention has advantageous characteristics due to the combination of the high elastic modulus, the high hardness and the high chemical stability of the fibers used, and by the high elastic limit and the ductility of the binder phase. Its remarkable mechanical properties, in particular its toughness, its resistance to wear, to creep, to rupture, to shock, to oxidation at high temperature, etc., make it a new material suitable for a large number of applications, such as cutting tools, wearing parts, structural elements such as motor, turbine, etc. For the production of complex parts, such as turbine blades and cutting inserts, which are exposed in use to high stresses at high temperatures, it is preferable that the whiskeys are oriented in the matrix. In general, it can be seen that the composite materials according to the invention have an increase in the stress intensity factor up to 2.5, and for tensile strength an increase by a factor of 10.
• Alumina fibers 1 ⁇ in diameter and 5mm long, whether or not covered by chemical vapor deposition with a 0.1 ⁇ titanium carbide layer mixed with titanium carbide, nickel and other elements sample 1 20% Al2O3 * + 80% (40% TiC + 40% Ni + 10% Mo2C + 8% Co + 2% Ru) sample 2 20% Al2O3 ** + 80% (40% TiC + 40% Ni + 10% Mo2C + 8% Co + 2% Ru)
• WC fibers 0.8 ⁇ in diameter and 8 mm long whether or not covered with a chemical vapor deposition of a 0.08 ⁇ thick layer of titanium carbide are mixed with WC, TiC , Ni and Mo2C: sample 1 20% WC * + 80% (42.5% WC + 42.5% TiC + 5% Mo2C + 12% Ni) sample 2 20% WC ** + 80% (42.5% WC + 42.5% TiC + 5% Mo2C + 12% Ni)
• fibers and protective coatings As additional examples, mention should also be made of (a) possible combinations of fibers and protective coatings, and (b) possible combinations of fibers and matrix or binder.
• fibers W, WC, Si3N4, Al2O3, BeO2, ZrO2, B4C, SiC, BN, B and C.
• TiC, TiN, WC, HfN and HfC matrix fiber (coating) Co WC (TiC), C (WC), B (WC) Co-Ni-Fe WC (TiC), Al2O3 (TiC), SiC (TiC), BN (TiC), WC (TiN), Al2O3 (TiN), BN (TiN), SiC (TiN), C (TiN), C (WC), B (WC), B (TiN) Ni-TiC WC (TiC), Al2O3 (TiC), SiC (TiC), BN (TiC), WC (TiN), Al2O3 (TiN), BN (TiN), SiC (TiN), C (TiAlON), C (TiN), C (WC), B (WC), B (TiN) "Super-alloy” (*) WC (TiC), Al2O3 (TiC), SiC (TiC), SiC (

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Ceramic Products (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)
• Powder Metallurgy (AREA)

Applications Claiming Priority (2)

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Citations (7)

• 1987
  • 1987-07-08 CH CH2599/87A patent/CH672640A5/fr not_active IP Right Cessation
  • 1987-09-30 DE DE198787114249T patent/DE298151T1/de active Pending
  • 1987-09-30 ES ES87114249T patent/ES2006432A4/es active Pending
  • 1987-09-30 EP EP87114249A patent/EP0298151A3/de not_active Withdrawn
• 1988
  • 1988-06-30 JP JP63161128A patent/JPS6431943A/ja active Pending

Patent Citations (7)

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