Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
  • C22C33/0207—Using a mixture of prealloyed powders or a master alloy
  • C22C33/0228—Using a mixture of prealloyed powders or a master alloy comprising other non-metallic compounds or more than 5% of graphite
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D19/00—Casting in, on, or around objects which form part of the product
  • B22D19/14—Casting in, on, or around objects which form part of the product the objects being filamentary or particulate in form
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/05—Mixtures of metal powder with non-metallic powder
  • C22C1/051—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor
  • C22C1/053—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor with in situ formation of hard compounds
  • C22C1/055—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor with in situ formation of hard compounds using carbon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/10—Alloys containing non-metals
  • C22C1/1036—Alloys containing non-metals starting from a melt
  • C22C1/1068—Making hard metals based on borides, carbides, nitrides, oxides or silicides
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
  • C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
  • C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
  • C22C33/0242—Making ferrous alloys by powder metallurgy using the impregnating technique
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C37/00—Cast-iron alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
• • 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
• • 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
  • B22F2998/10—Processes characterised by the sequence of their steps
• • 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
  • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/10—Alloys containing non-metals
  • C22C1/1036—Alloys containing non-metals starting from a melt
  • C22C1/1047—Alloys containing non-metals starting from a melt by mixing and casting liquid metal matrix composites
  • C22C1/1052—Alloys containing non-metals starting from a melt by mixing and casting liquid metal matrix composites by mixing and casting metal matrix composites with reaction
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12535—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.] with additional, spatially distinct nonmetal component
  • Y10T428/12576—Boride, carbide or nitride component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12806—Refractory [Group IVB, VB, or VIB] metal-base component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12861—Group VIII or IB metal-base component
  • Y10T428/12951—Fe-base component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/25—Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
  • Y10T428/256—Heavy metal or aluminum or compound thereof

Definitions

• the present invention relates to a hierarchical composite material having improved resistance to the combined stress wear / impact.
• the composite comprises a metal matrix of cast iron or steel, reinforced by a particular structure of titanium carbide.
• Hierarchical composites are a well-known family in the science of materials.
• the reinforcement elements must be present in sufficient thickness to withstand severe and simultaneous stress in terms of wear and impact.
• the composite wearing parts reinforced with titanium carbide created in situ are one of the possibilities mentioned in this article in section 2.4. Wear parts in this case are nonetheless made using exclusively powders as part of a self-propagating reaction at high temperature (SHS), where the titanium reacts exothermically with carbon to form titanium carbide in a matrix based on a ferrous alloy, also introduced in powder form.
• SHS self-propagating reaction at high temperature
• This type of synthesis makes it possible to obtain micrometric globular titanium carbide dispersed homogeneously within a matrix of a ferrous alloy (FIG 12A (c)).
• the article also describes very well the difficulty of controlling such a synthesis reaction.
• the document EP 1 450 973 discloses a wearing part reinforcement made by placing in the mold intended to receive the casting metal, an insert consisting of a mixture of powders which react with each other thanks to the heat supplied by the metal during casting at high temperature (> 1400 ° C.). The reaction between the powders is initiated by the heat of the casting metal.
• the powders of the reactive insert after reaction of the SHS type, will create a porous mass (conglomerate) of hard particles of ceramics formed in situ; this porous mass, once formed and still at a very high temperature, will be immediately infiltrated by the casting metal.
• WO 02/053316 discloses in particular a composite part obtained by SHS reaction between titanium and carbon in the presence of binders, which makes it possible to fill the pores of the skeleton constituted by titanium carbide.
• the parts are made from powders put in compression in a mold. The hot mass obtained after SHS reaction remains plastic and is compressed in its final form.
• EP 0 852 978 A1 and US 5,256,368 disclose a similar technique related to the use of pressurized pressure or reaction to result in a reinforced workpiece.
• GB 2 257 985 discloses a method for producing a titanium carbide reinforced alloy by metallurgy of powders. This is in the form of globular microscopic particles less than 10 microns in size dispersed within the porous metal matrix.
• the reaction conditions are chosen so as to propagate an SHS reaction front in the part to be produced.
• the reaction is ignited by a burner and there is no infiltration by an external casting metal.
• US 6,099,664 discloses a composite part comprising titanium boride and optionally titanium carbide.
• the powder mixture comprising eutectic ferrotitanium, is heated by a burner so as to form exothermic reactions of boron and titanium.
• a reaction front is propagating through the room.
• US 6,451,249 B1 discloses a reinforced composite part comprising a ceramic skeleton optionally with carbides which are bonded together by a metal matrix as a binder and which contains a thermite capable of reacting according to a SHS reaction to produce the heat of fusion necessary for the agglomeration of the ceramic granules.
• WO 93/03192 and US 4,909,842 also disclose a method for producing an alloy comprising particles of titanium carbide finely dispersed within a metal matrix. This is again a powder metallurgy technique and not a technique of infiltration by casting in a foundry.
• US 2005/045252 discloses a hierarchical composite with a periodic and three-dimensional hierarchical structure of hard and ductile metal phases arranged in strips. Other techniques are also well known to those skilled in the art, such as the addition of hard particles in the liquid metal, in the melting furnace, or techniques of reloading or reinforcements by inserts . All these techniques, however, have various disadvantages that do not allow to achieve a hierarchical composite reinforced with titanium carbide practically without limitation of thickness and having good resistance to shocks and chipping and very economically.
• the present invention proposes to overcome the disadvantages of the state of the art and discloses a hierarchical composite material with improved wear resistance while maintaining good impact resistance. This property is obtained by a particular reinforcement structure which takes the form of a macro-microstructure comprising discrete millimetric zones concentrated in micrometric globular particles of titanium carbide.
• the present invention also provides a hierarchical composite material comprising a particular structure of titanium carbide obtained by a particular method.
• the present invention further provides a method for obtaining a hierarchical composite material having a particular structure of titanium carbide.
• the present invention discloses a hierarchical composite material comprising a ferrous alloy reinforced with titanium carbides according to a defined geometry in which, said reinforced portion comprises an alternating macro-microstructure of millimetric zones concentrated in micrometric globular particles of separated titanium carbide millimetric zones substantially free of micrometric globular particles of titanium carbide, said micrometrically concentrated micrometrically proportioned particles of titanium carbide forming a microstructure in which the micrometric interstices between said globular particles are also occupied by said ferrous alloy.
• the hierarchical composite material comprises at least one or a suitable combination of the following characteristics:
• said concentrated millimetric zones have a concentration of titanium carbides greater than 36.9% by volume
• said reinforced portion has an overall titanium carbide content of between 16.6 and 50.5% by volume;
• micrometric globular particles of titanium carbide have a size of less than 50 ⁇ m
• micrometric globular particles of titanium carbide have a size of less than 20 ⁇ m; said zones concentrated in globular particles of titanium carbide comprise 36.9 to 72.2% by volume of titanium carbide;
• said millimetric zones which are concentrated in titanium carbide, have a size ranging from 1 to 12 mm;
• said millimetric zones which are concentrated in titanium carbide, have a size ranging from 1 to 6 mm;
• said concentrated zones made of titanium carbide have a dimension varying from 1.4 to 4 mm; said composite is a wear part.
• the present invention also discloses a method of manufacturing the hierarchical composite material according to any one of claims 1 to 10 comprising the following steps: - provision of a mold having the footprint of the hierarchical composite material with a geometry predefined reinforcement;
• the method comprises at least one or a suitable combination of the following characteristics:
• the mixture of compacted powders of titanium and carbon comprises a powder of a ferrous alloy
• the present invention also discloses a hierarchical composite material obtained according to the method of any one of claims 11 to 13.
• the present invention also discloses a tool or a machine comprising a hierarchical composite material according to any one of claims 1 to 10 or according to claim 14.
• FIG. 1 shows a diagram of the reinforcement macro-microstructure within a steel or cast iron matrix constituting the composite.
• the clear phase represents the metal matrix and the dark phase, concentrated zones of globular titanium carbide.
• the photo is taken at low magnification under an optical microscope on an unpicked polished surface.
• FIG. 2 represents the limit of a concentrated zone of globular titanium carbide towards a zone generally free of globular titanium carbide at higher magnification. We also note the continuity of the metal matrix on the whole of the room. The space between micrometric particles of titanium carbide
• micrometric interstices or pores is also infiltrated by the casting metal (steel or cast iron).
• the photo is taken at low magnification under an optical microscope on an unpicked polished surface.
• Figure 3a-3h shows the method of manufacturing the hierarchical composite according to the invention.
• step 3a shows the device for mixing titanium and carbon powders
• step 3b shows the compaction of the powders between two rollers followed by crushing and sieving with recycling of the fine particles
• FIG. 3c shows a sand mold in which a dam has been placed to contain the granules of compacted powder at the site of reinforcement of the hierarchical composite
• FIG. 3d shows an enlargement of the reinforcement zone in which the compacted granules comprising the precursor reagents of TiC are located;
• step 3e shows the casting of the ferrous alloy in the mold
• FIG. 3f shows the hierarchical composite resulting from the casting
• FIG. 3g shows an enlargement of the zones with a high concentration of micrometric particles (globules) of TiC - this diagram represents the same zones as in FIG. 4;
• FIG. 3h shows an enlargement within the same area with high concentration of TiC globules - the micrometer globules are individually surrounded by the casting metal.
• FIG. 4 represents a binocular view of a polished, untouched surface of the macro- microstructure according to the invention with millimetric zones (in light gray) concentrated in micrometric globular titanium carbide (TiC globules).
• the dark part represents the metal matrix (steel or cast iron) filling both the space between these micrometric globular titanium carbide concentrated zones but also the spaces between the globules themselves (see Fig. 5 & 6).
• Figures 5 and 6 show SEM electron microscope views of micrometric globular titanium carbides on polished and untouched surfaces at different magnifications. We see that in this particular case most of the globules of titanium carbide have a size less than 10 microns.
• Figures 7 and 8 show views of micrometric globular titanium carbides at different magnifications, but this time on fracture surfaces taken under SEM electron microscope. It can be seen that the globules of titanium carbide are perfectly incorporated in the metal matrix. This proves that the casting metal completely infiltrates (impregnates) the pores during casting once the chemical reaction between titanium and carbon is initiated.
• Figures 9 and 10 are spectra of analysis of Ti as well as Fe in a reinforced part according to the invention. This is a "mapping" of Ti and Fe distribution by EDX analysis, taken electron microscopically from the fracture surface shown in Figure 7. The light spots in Figure 9 show the Ti and the Clear spots in Figure 10 show the Fe (thus the pores filled by the casting metal).
• FIG. 11 shows, at high magnification, a fracture surface taken by SEM electron microscope. with an angular titanium carbide which formed by precipitation, in an area generally free of titanium carbide globules.
• Figure 12 shows, at high magnification, a fracture surface taken by electron microscope SEM with a gas bubble. We always try to limit as much as possible this kind of defect.
• Fig. 13 shows an arrangement of anvils in a vertical axis crusher which has been used to perform comparative tests between wearing parts having reinforced areas with bulky inserts and parts having reinforced areas with the macro-microstructure of the present invention.
• FIG. 14 shows a block diagram illustrating the macro-microstructure according to the present invention already partially illustrated in FIG. 3.
• SHS reaction or "self-propagating high temperature synthesis” is a self-propagating high-temperature synthesis reaction in which reaction temperatures generally greater than 1500 0 C, or 2000 0 C.
• reaction temperatures generally greater than 1500 0 C, or 2000 0 C.
• the reaction between titanium powder and carbon powder to obtain titanium carbide TiC is highly exothermic. Only a little energy is needed to initiate the reaction locally. Then, the reaction will spontaneously propagate to the entire mixture of reagents thanks to the high temperatures reached. After initiation of the reaction, there is a reaction front which propagates spontaneously (self-propagated) and which makes it possible to obtain titanium carbide from titanium and carbon.
• the titanium carbide thus obtained is said to be "obtained in situ" because it does not come from the cast ferrous alloy.
• the reagent powder mixtures comprise carbon powder and titanium powder and are compressed into plates and then crushed in order to obtain granules whose size varies between 1 and 12 mm, of preferably from 1 to 6 mm, and particularly preferably from 1.4 to 4 mm. These granules are not 100% compacted. They are generally compressed between 55 and 95% of the theoretical density. These granules are easy to use / handle (see Fig. 3a-h).
• the millimetric granules of mixed carbon and titanium powders constitute the precursors of the titanium carbide to be created and make it possible to easily fill mold parts of various or irregular shapes. These granules can be held in place in the mold 15 by means of a dam 16, for example. The shaping or assembly of these granules can also be done using an adhesive.
• the hierarchical composite according to the present invention, and in particular the macro-microstructure of reinforcement that can also be called alternating structure of concentrated zones in micrometric globular particles of titanium carbide separated by zones which are practically free, is obtained by the reaction in the mold 15 granules comprising a mixture of powders of carbon and titanium.
• This reaction is initiated by the heat of casting of the cast iron or steel used to pour the whole piece, and thus both the unreinforced part and the reinforced part (see Fig. 3e).
• the casting thus triggers an exothermic reaction of self-propagating synthesis at high temperature of the mixture of powders of carbon and titanium compacted in the form of pellets (self-propagating high-temperature synthesis SHS) and previously placed in the mold 15.
• SHS self-propagating high-temperature synthesis
• This high temperature synthesis allows easy infiltration of all interstices millimetric and micrometric by cast iron or casting steel (Fig. 3g & 3h). By increasing the wettability, the infiltration can be done on any thickness of reinforcement. It advantageously makes it possible, after SHS reaction and infiltration by an external casting metal, to create zones with a high concentration of micrometric titanium carbide globular particles (which could also be called nodule clusters), which zones having a size of the order of a millimeter or a few millimeters, and which alternate with areas substantially free of globular titanium carbide. Areas with low carbide concentration are actually millimeter spaces or interstices 2 between the granules infiltrated by the casting metal. We call this superstructure a macro-microstructure reinforcement.
• the areas where these granules were found show a concentrated dispersion of micrometric globular particles 4 of TiC (globules) whose micrometric interstices 3 have also been infiltrated by the casting metal, which is here cast iron or steel. It is important to note that the millimetric and micrometric interstices are infiltrated by the same metal matrix as that which constitutes the non-reinforced part of the hierarchical composite, which allows a total freedom of choice of the casting metal.
• the areas with a high concentration of titanium carbide are composed of micrometric globular TiC particles in a large percentage (between about 35 and 75% by volume) and ferrous alloy infiltration.
• micrometric globular particles are meant globally spheroidal particles which have a size ranging from ⁇ m to a few tens of ⁇ m, at most. We also call them TiC globules. The vast majority of these particles having a size less than 50 microns and even 20 microns, or even 10 microns. This globular form is characteristic of a method for obtaining titanium carbide by self-propagating SHS synthesis (see Fig. 6).
• the reinforced structure according to the present invention can be characterized by optical or electronic microscope.
• the macro-microstructure of reinforcement is visible visually or at low magnification.
• At high magnification in areas with a high concentration of titanium carbide, globular 4 titanium carbide with a volume percentage in these areas of between about 35 and about 75%, depending on the level of compaction of the granules, can be distinguished. the origin of these areas
• Titanium carbide will be obtained by the reaction between the carbon powder and the titanium powder. These two powders are mixed homogeneously. Titanium carbide can be obtained by mixing 0.50 to 0.98 moles of carbon to 1 mole of titanium, the stoichiometric composition Ti + 0.98 C ⁇ TiC 0 .98 being preferred.
• the process for obtaining the granules is illustrated in FIG. 3a-3h.
• the granules of carbon / titanium reagents are obtained by compaction between rollers 10 in order to obtain strips that are then crushed in a crusher 11.
• the mixture of the powders is made in a mixer 8 consisting of a tank equipped with blades , to promote homogeneity.
• the mixture then passes into a granulation apparatus through a hopper 9.
• This machine comprises two rollers 10 through which the material is passed. Pressure is applied to these rollers 10, which compresses the material. A strip of compressed material is obtained at the outlet, which is then crushed in order to obtain the granules.
• the granules obtained from the raw material Ti + C are porous. This porosity varies from 5% for highly compressed granules, to 45% for slightly compressed granules. In addition to the level of compaction, it is also possible to adjust the particle size distribution of the granules and their shape during the operation of crushing strips and sieving Ti + C granules. Unwanted size fractions are recycled at will (see Fig. 3b).
• the granules obtained generally have a size between 1 and 12 mm, preferably between 1 and 6 mm, and particularly preferably between 1.4 and 4 mm. Realization of the reinforcement zone in the hierarchical composite according to the invention
• the granules are made as described above. To obtain a three-dimensional structure or superstructure / macro-microstructure with these granules justifying the hierarchical composite name, they are available in the areas of the mold where it is desired to reinforce the part. This is achieved by agglomerating the granules either by means of an adhesive, or by confining them in a container, or by any other means (dam 16).
• the bulk density of the stack of Ti + C granules is measured according to ISO 697 and depends on the level of compaction of the bands, the granulometric distribution of the granules and the crushing mode of the bands, which influences the shape of the granules .
• the bulk density of these Ti + C granules is generally of the order of 0.9 g / cm 2 to 2.5 g / cm 3 depending on the level of compaction of these granules and the density of the stack. Before reaction, there is therefore a stack of porous granules composed of a mixture of titanium powder and carbon powder.
• the reinforcement was carried out by placing granules in a metal container of 100x30x150 mm, which is then placed in the mold at the place of the piece that is wish to strengthen. Then we cast the steel or cast in this mold.
• Example 1 it is intended to produce a part whose reinforced zones comprise an overall volume percentage of TiC of about 42%.
• a band is produced by compaction at 85% of the theoretical density of a mixture of C and Ti. After crushing, the granules are sieved to obtain a pellet size of between 1.4 and 4 mm. A bulk density of the order of 2.1 g / cm 3 (35% space between the granules + 15% porosity in the granules) is obtained. The granules are placed in the mold at the location of the part to be reinforced, which thus comprises 65% by volume of porous granules.
• a chromium cast iron (3% C, 25% Cr) is then cast at about 1500 ° C. in a non-preheated sand mold.
• the reaction between Ti and C is initiated by the heat of melting. This casting is done without a protective atmosphere.
• a part whose reinforced areas comprise an overall volume percentage of TiC of about 30%.
• a 70% compaction band is made of the theoretical density of a mixture of C and Ti.
• the granules are sieved to obtain a pellet size of between 1.4 and 4 mm.
• the granules are placed in the part to be reinforced, which thus comprises 55% by volume of porous granules.
• 55% by volume of zones with a high concentration of approximately 53% of globular titanium carbide are obtained, ie approximately 30% by global volume of TiC in the reinforced part of the piece of wear.
• Example 3 it is intended to produce a part whose reinforced zones comprise an overall volume percentage of TiC of about 20%.
• a band is made by compaction at 60% of the theoretical density of a mixture of C and Ti. After crushing, the granules are sieved so as to obtain a granule size of 1 and 6 mm. A bulk density of the order of 1.0 g / cm 3 (55% of space between the granules + 40% of porosity in the granules) is obtained.
• the granules are placed in the part to be reinforced, which thus comprises 45% by volume of porous granules. After reaction, in the reinforced part 45% by volume of concentrated zones with approximately 45% of globular titanium carbide is obtained, ie 20% by global volume of TiC in the reinforced part of the wear part.
• Example 2 it was sought to attenuate the intensity of the reaction between carbon and titanium by adding a ferrous alloy powder.
• a wear part whose reinforced areas comprise an overall volume percentage of TiC of about 30%.
• a band is produced by compaction at 85% of the theoretical density of a mixture by weight of 15% of C, 63% of Ti and 22% of Fe. crushing, the granules are sieved so as to obtain a granule size of between 1.4 and 4 mm.
• a bulk density of the order of 2 g / cm 3 (45% of space between the granules + 15% of porosity in the granules) is obtained.
• the granules are placed in the part to be reinforced, which thus comprises 55% by volume of porous granules. After reaction, 55% by volume of zones with a high concentration of approximately 55% of globular titanium carbide, ie 30%, are obtained in the reinforced part.
• FIG. 13 In this machine, the inventor alternately disposed an anvil comprising an insert according to the state of the art surrounded on both sides of a unreinforced anvil, and an anvil with a zone reinforced by a macro-microstructure according to the present invention, also framed by two unreinforced reference anvils.
• a performance index has been defined with respect to an unreinforced anvil and with respect to a given type of rock. Although extrapolation to other types of rock is not always easy, we have nevertheless tried a quantitative approach to observed wear.
• the performance index is the ratio of the wear of the non-reinforced reference anvils relative to the wear of the reinforced anvil.
• An index of 2 therefore means that the reinforced part has worn out twice as fast as the reference parts. We measure the wear in the working part (mm worn), where is the reinforcement.
• the performance of the insert according to the state of the art are similar to those of the macro-microstructure of the invention, except for the compaction rate of 85% of the granules which shows a slightly higher performance.
• the same performance is obtained as with 1100 g of Ti + C powder in the form of an insert. Since this mixture costs around 75 Euro / kg in 2008, the advantage provided by the invention is measured.
• the porous millimetric granules are crimped in the infiltration metal alloy. These millimetric granules are themselves composed of microscopic particles with a globular tendency, TiC, also crimped in the metal alloy infiltration. This system makes it possible to obtain a composite part with a macrostructure within which there is an identical microstructure on a scale approximately a thousand times smaller.
• this material comprises small globular particles of titanium carbide, hard and finely dispersed in a metal matrix which surrounds them, makes it possible to prevent the formation and propagation of cracks (see FIGS. ).
• the cracks generally originate at the most fragile places, which are in this case the TiC particle, or the interface between this particle and the infiltration metal alloy. If a crack originates at the interface, or in the micrometric particle of TiC, the propagation of this crack is then impeded by the infiltration alloy which surrounds this particle.
• the toughness of the infiltration alloy is greater than that of the TiC ceramic particle. The crack needs more energy to pass from one particle to another to cross the micrometric spaces that exist between the particles. Another reason to explain the best impact resistance is a more rational implementation of titanium carbide to achieve adequate reinforcement.
• the reaction between Ti and C is strongly exothermic.
• the rise in temperature causes degassing of the reagents, that is to say volatile materials included in the reagents (H 2 O in carbon, H 2 , N 2 in titanium).
• the higher the reaction temperature the greater this clearance is important.
• the granular technique makes it possible to limit the temperature, to limit the gaseous volume and allows an easier evacuation of the gases and thus to limit the gas defects (see Fig. 12 with undesirable gas bubble).
• the coefficient of expansion of the TiC reinforcement is lower than that of the ferrous alloy matrix (coefficient of expansion of the TiC: 7.5 10 ⁇ 6 / K and the ferrous alloy: approximately 12.0 10 "6 / K).
• This difference in the expansion coefficients has the consequence of generating tensions in the material during the solidification phase and also during the heat treatment, if these tensions are too great, cracks can appear in the part and lead to the rejection of this material.
• a small proportion of TiC reinforcement (less than 50% by volume) is used, resulting in less stress in the workpiece. More ductile between the micrometric globular particles of TiC alternating zones of low and high concentration makes it possible to better assume any local tensions.
• the boundary between the reinforced portion and the non-reinforced portion of the hierarchical composite is not abrupt because there is a continuity of the metal matrix between the reinforced portion and the unreinforced part, which makes it possible to protect it against a complete tearing off of the reinforcement.

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