Ceramic composite comprising sic-diamond joined to another part

This invention relates to a method for joining parts of ceramic composites comprising at least one ceramic material and at least one superhard material with at least one other part. In particular, the invention relates to a method of combining silicon carbide-diamond composites with other materials, and materials and tools containing such combined materials.

BACKGROUND OF THE INVENTION [0002] Ceramic materials, such as, for example, SiC, Si3N4, Al2O3, ZrO, are materials that are usually hard, refractory and relatively chemically inert, and are therefore used in a variety of applications, such as abrasion resistant parts, ballistic armor, cutting tools and electronic parts. The incorporation of superhard phases such as diamond and cubic boron nitride (cBN) into the ceramic material can significantly increase the average hardness, abrasion resistance and thermal conductivity of the composite material. For example, patents US 6,447,852 and US 6,709,747 disclose a type of material comprising SiC and diamond as well as small amounts of silicon or other materials, as well as a method for their production. Different forms of this material contain different volume fractions and diamond size distributions, wherein the formulation can be designed for various applications. The applications of this material are as diverse as the thermal management of electronic devices, nozzles for water jets and inserts for drills in stone. The shapes of ceramic-diamond composite elements used in these and other applications can be complex and almost always need to be connected to at least one other part to form an integrated element. In some applications, such as stone drilling, the strength of such joints must be very high, so that the ceramic-diamond composite part does not detach from the element during operation. The shapes of ceramic-diamond composite elements used in these and other applications can be complex and almost always need to be connected to at least one other part to form an integrated element. In some applications, such as stone drilling, the strength of such joints must be very high, so that the ceramic-diamond composite part does not detach from the element during operation. The shapes of ceramic-diamond composite elements used in these and other applications can be complex and almost always need to be connected to at least one other part to form an integrated element. In some applications, such as stone drilling, the strength of such joints must be very high, so that the ceramic-diamond composite part does not detach from the element during operation.

[0003] Combining the high strength ceramic material elements with other elements is a complicated and specialized technique and typically can not be borrowed from conventional joining techniques, such as, for example, hard soldering using a gas burner in the air. Limited success can be achieved using highly specialized reactive hard solders that have been specially designed for ceramic materials and for which special atmospheres may be needed. These methods are usually quite expensive and are not suitable for mass production or cost sensitive applications.

[0004] The use of brazing for joining parts is well known in the art as well as the surface treatment of parts to be combined. Brazing alloys include materials with a lower melting point than each of the connection parts. The brazing alloys are typically in the form of a paste or film and may be placed on one or both of the joined portions prior to forming the joint. Generally compatible fluxes are also generally needed. The surfaces of the parts that are involved in the joining are referred to herein as the joint surfaces.

[0005] The ScD material can be described as a material comprising diamond particles connected in a silicon carbide matrix. There are various disclosures in this field devoted to such material, including US Patent No. 6,709,747, US Patent No. 6,447,852 and US Patent No. 6,868,848.

[0006] ScD material is relatively new, there are no relevant disclosures in this field regarding the attachment of ScD material to metal structural members. In this field of technology, active hard soldering combining ceramic materials is well known. Below is an excerpt from "Vacuum brazing of ceramics and graphite to metals" by HR Prabhakar Bangalore Plasmatek Pvt.Ltd, 129, Block-14, Jeevanmitra Colony I-Phase, Bangalore 560 078

But combining ceramic materials with metals and themselves is not easy. There are basically two problems. First, ordinary brazing fillers do not wet the surface of the ceramic material. Secondly, there is a large difference in thermal coefficients of thermal expansion of metals and ceramic material. This causes huge stresses in the brazing process that can lead to cracks. Special techniques have been developed for brazing ceramics. Molybdenum-manganese metallization is a standard practice for brazing ceramic materials. In this case, the paint from refractory molybdenum metal with 10% manganese is applied to the ceramic material and sintered all at 1400 ° C. In this process, the manganese oxidizes and diffuses in the ceramic material to form a transition layer between the ceramic material and the molybdenum layer. This reduces the thermal mismatch between ceramic and molybdenum. Then it is protected from oxidation by nickel coating. The brazing is then carried out using conventional filler materials either in a vacuum or in an inert gas atmosphere.

[0007] Active hard brazing is a relatively new technique. A family of brazing alloys called active brazing alloys is made by adding a low percentage of titanium or vanadium to conventional filler materials. Brazing is carried out under high vacuum conditions under clean conditions. During brazing, titanium is oxidized by a ceramic material to form titanium oxides and give off a number of aluminum atoms. This intermediate layer creates a kind of chemical bridge between the ceramic material and the metal. An alternative method is to have a titanium coating on the ceramic material and then perform a regular hard brazing. At high temperatures, titanium also reacts with ceramic materials and other metals. Normal brazing alloys wet the surface of the titanium well, leading to good brazing. With regard to the brazing of ultrahard materials to the tool, the method known in the art is the use of active brazing material (containing carbide forming constituents: Ti, Cr, Mo, etc. such as TiCuSil) and heating to melt under high vacuum, <10^-5 mBar.

[0008] Combining composite materials comprising ceramic materials and superhard materials is usually more complicated by the presence of a superhard material whose surface area can undergo phase change during the production of the composite, especially if the process requires the use of heat, as is usually the case. This is because super-hard phases are usually metastable under pressure conditions commonly used in such processes and are easily transformed into softer phases at elevated temperatures. For example, a diamond tends to convert to graphite (or "graphitize") at temperatures above 700 degrees Celsius (° C) in the air. The surface of the combination of such materials therefore typically includes an exposed superhard material (like a diamond), at least a part of the surface of this material has been transformed into a softer phase (e.g. graphite) as well as the exposure of the ceramic material. Every

The exposed graphite phases or other soft phases on the interface surface will tend to reduce the strength of the connection. Any connection method that requires the use of a significant amount of heat, especially in the air, risks further conversion of the exposed metastable super-elastic phases to the softer phase.

[0009] US Patent Nos. 5,500,248 and 5,647,878 disclose inserts for diamond tools that can be brazed in air. The disclosures in these references are not optimized for joining parts containing ceramic and superhard material.

[0010] There is therefore a need for a method for joining parts of ceramic composites comprising at least one ceramic material and at least one superhard material for at least one other portion.

SUMMARY OF THE INVENTION [0011] A method for combining portions of ceramic composites comprising at least one ceramic and at least one superhard material into at least one other part is disclosed, the method comprising the steps of; • treating one or more surfaces of a composite part combination ceramic; and • disposing on one or more of the treated surfaces, or parts thereof, a material capable of binding to a portion of the ceramic composite as well as to at least one other portion after applying sufficient heat.

[0012] The treatment may be a roughening, etching or otherwise increasing the surface area for the surface of the combination of parts from the ceramic composite.

[0013] Preferably, the method is used in an oxidizing environment. Most preferably, the obtained bond strength between a portion of a ceramic composite and at least one other portion is similar to or greater than the bond strength between a superhard material and a ceramic material in a part of a ceramic composite.

[0014] The ceramic composite portion contains SiC. The superhard material is a diamond.

In one embodiment of the present invention, the surface treatment of joining parts of the ceramic composite includes treatment with an acid or combination of acids such that the exposed ceramic on the surface or surfaces to be bonded is roughed (etched) (i.e., exposed surface area of ​​the superhard surface on the surface of the connection is increased, as measured by any method well known in the art). In addition, any graphite present on the exposed one or more diamond surfaces can be substantially removed. [0016] Preferably, the surface treatment is carried out in two steps. First, it is possible to use an acid selected from HCl, H2SO4, HF and HNO3 to roughen or etch a portion of the non-bolted connection surface (e.g., exposed SiC). HF is preferably used and can be heated. This is preferably followed by a hot treatment (20 - 150 ° C) with a second acid selected from strong oxidizing acids, e.g. chromic acid, fuming sulfuric acid and solid KNO3 and / or HClO4. A combination (NaOH + KNO3) may also be used, although a simple wet chemical method, preferably with chromic acid, is most preferably used. The other one

The purpose of the step is to remove any graphite that may be present at the interface surface and on exposed diamond surfaces, in particular when the superhard material is a diamond.

[0017] The material disposed on the treated surface / surfaces comprises separate layers of material that can be applied successively to the surface to be joined. These layers are:

i) a fastening layer, ii) a hard-soldered layer, and iii) an oxidation resistant layer (compatible with hard solder).

The superhard material is a diamond, the fixing layer preferably comprises a carbide (most preferably TiC, but also any chemically bonded carbide, such as chromium carbide) increased on a portion of the exposed one or more diamond surfaces on the joint surface. The carbide, preferably TiC, can be applied to a significant portion of the interface by means of the conventional chemical vapor deposition (CVD) method known in the art. This will cause any exposed diamond to be coated by and chemically bonded to the carbide layer, preferably TiC.

[0019] The attachment layer is sufficiently thick to form a strong bond (at least 0.1 micron, preferably at least 0.2 micron, more preferably at least 0.3 micron, most preferably at least 0.4 micron) and not so thick to be exfoliated (e.g., less than about 8 microns, preferably less than about 7 microns, more preferably less than about 6 microns, most preferably less than about 5 microns).

[0020] The hard-to-braze layer is preferably applied to the surface of the joint over the fastening layer. The hard-soldered layer is preferably composed of a material formulation selected for a good bond with the fixing layer and comprises a refractory metal selected from W, Mo, Cr, Ni, Ta, Au, Pt, Pd, Nb or any combination or alloy thereof ( most preferably W), deposited on a mounting layer arranged on (contained on) a substantial portion of one or more superhard surfaces on the interface surface and on a substantial part of any part of the surface of the non-coated connection layer. Preferably, the metallic tungsten is used as a hard-soldered brazing layer due to its well-known tendency to be wetted by molten hard fusion and its high melting point, which ensures that it will not be removed or deformed at an elevated temperature, which may be required for subsequent brazing. Molybdenum is an alternative suitable material for the hard-soldered layer. The tungsten layer should have at least about 0.1 microns, preferably at least 0.5 microns thick and less than about 20 microns, preferably less than 10, more preferably less than 2 microns thick. A standard physical vapor deposition (PVD) method known in the art may be used to deposit the tungsten layer. Alternatively, tungsten can be applied using CVD. The tungsten layer should have at least about 0.1 microns, preferably at least 0.5 microns thick and less than about 20 microns, preferably less than 10, more preferably less than 2 microns thick. A standard physical vapor deposition (PVD) method known in the art may be used to deposit the tungsten layer. Alternatively, tungsten can be applied using CVD. The tungsten layer should have at least about 0.1 microns, preferably at least 0.5 microns thick and less than about 20 microns, preferably less than 10, more preferably less than 2 microns thick. A standard physical vapor deposition (PVD) method known in the art may be used to deposit the tungsten layer. Alternatively, tungsten can be applied using CVD.

[0021] Because materials usually suitable for use in a hard-soldered layer, such as tungsten and molybdenum, may be susceptible to surface oxidation at brazing temperatures and may also be affected by fluxes used with solder (which could reduce their strength). the ability to wet through hard fused), a further oxidation resistant layer is deposited comprising elements selected from Ag, Sn, Au, Pt (but preferably Ag) or their alloys, or with each other and / or other metals, such as bronze or brass or alloy for brazing is deposited on a hard-soldered layer. This is to eliminate the effects of oxidation

The surface area has the ability to braze a hard product. PVD can be used to deposit an oxidation resistant layer (Ag). Alternatively, a wet chemical technique for the deposition of silver can be used.

[0022] The oxidation resistant layer (Ag) should preferably be wettable by the braze and be substantially coarse.

[0023] The hard-soldered layer should preferably be wettable by a braze, be substantially coarse, and should not melt to a large extent with the braze.

[0024] The present invention provides an article comprising a part of a ceramic composite comprising a ceramic material and at least one superhard material bonded to at least one other portion, the article being in accordance with claim 1.

[0025] Preferably, the connection surface of a portion of the ceramic composite has been treated to roughen, etch or otherwise increase the surface area of ​​the joint.

[0026] Preferably, the article is an insert for use in the auger, rotary drills, impact drills or a pick, where at least a portion of the insert's working surface consists of a ScD material. The upper part of the insert can be symmetrical or asymmetrical.

[0027] Alternatively, the article may be a PDC cutting shear, wherein at least a portion of the insert's working surface consists of ScD.

[0028] Alternatively, the article may be an insert for securing the indicator, wherein at least a portion of the insert's working surface consists of ScD.

[0029] Preferably, the insert is a shaped insert. The insert may comprise a substantially cylindrical body portion and a chisel-shaped upper portion.

[0030] Alternatively, the insert may comprise a substantially cylindrical body portion and an upper semi-circular upper portion.

[0031] Alternatively, the insert may comprise a substantially cylindrical body portion and an upper, substantially bullet-shaped portion.

[0032] The insert may comprise a substantially cylindrical body portion and a substantially symmetrical or asymmetrical upper portion.

According to a third aspect of the present invention there is provided an abrasion-resistant element comprising a metal body portion connected to a portion of a ceramic interface at the interface, wherein a part of the ceramic composite comprises a superhard material and a ceramic material, the double layer being bonded to the surface of the composite part. near the interface, wherein the double layer comprises a first carbide-forming element layer and a second layer of a high melting point metal selected from W, Mo, Cr, Ni, Ta, Au, Pt, Pd or any of them. of a combination or alloy thereof, the second layer being substantially free of the carbide-forming element of the first layer.

According to a fourth aspect of the present invention, there is provided an abrasion-resistant element comprising a metal body portion associated with a part of the ceramic composite at the interface, the portion of the ceramic composite comprising superhard material and material

The first carbide-forming layer of the carbide-forming element and the second layer comprising the metal selected from W, Mo, Cr, Ni, Ta, Au, Pt, Pd, or any combination or alloy thereof is found on intermediate surfaces of metal parts and parts of the ceramic composite at the interface.

[0035] Preferably, the second layer is bonded to the first layer and the first layer is bonded to the surface of a portion of the ceramic composite.

[0036] Preferably, the carbide-forming element is selected from Ti, Cr and Mo.

[0037] Preferably, the metal with a high melting point is W.

[0038] The superhard material is a diamond and the ceramic material contains SiC.

[0039] Preferably, the thickness of the first carbide layer is at least about 0.1 micron, preferably at least about 0.3 micron, most preferably about 0.4 micron and less than 20 micron, preferably less than 10 micron, more preferably less than 5 microns. The average thickness of the first carbide layer can be from 0.1 to 1 micron, more preferably 0.3 to 1 micron and most preferably 0.4 to 1 micron.

[0040] Preferably, the element forming the carbide of the first layer is not substantially present at the interface in a form other than carbide.

[0041] Preferably, the body portion of the wear-resistant metal member comprises tungsten carbide or steel, most preferably tungsten carbide.

[0042] Preferably, the surface of a portion of the ceramic composite near the interface is substantially free of graphite or non-diamond carbon.

[0043] Preferably, the abrasion resistant member is a tool that is preferably a rotary drill, an attacking tool or a pickaxe.

[0044] The prior art does not disclose a step of treating one or more surfaces of joining parts of a ceramic composite, which step leads to significant advantages for the materials in question.

[0045] Furthermore, the present invention discloses that when the ceramic material is present in the parts to be joined, the TiC layer is separated from the brazeable layer. The state of the art positively does not reveal separate layers. In the prior art, the TiC layer is very thin (0.1 microns) with the presence of Ti-not-Ti in the In-W mixture. The present invention discloses a "thick" TiC layer, which results in improved stress limitations on the interface with the superhard material. In addition, the present invention offers better protection of the superhard phase, such as diamond, against the brazing material. Finally, according to the disclosure of the present invention, it allows a greater degree of freedom in the selection of the hard-soldered layer. In particular,

[0046] The invention will now be described with reference to the following non-limiting example.

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EXAMPLE [0047] A portion of a SiC-diamond composite material containing 60 vol% diamond (material ScD 020902-C SNMN4404) connects to a part containing sintered tungsten carbide (cubes 5 mm x 5 mm cut from a 8% Co plate in a toilet used as an abrasive surface).

Surface preparation [0048] The surface of the combination of SiC-diamond composite parts was prepared by acid treatment. This was done in two stages. First, HCl / HF was used (other acids, such as H2SO4 and HNO3 could also be used) to roughen or etch a portion of the non-tie surface of the junction (i.e., mainly exposed SiC). This was followed by treatment with hot (20-150 ° C) chromic acid to remove substantially any graphite that may be present on the interface surface and in particular on exposed diamond surfaces.

Coating [0049] Next, three different layers of different materials were successively applied to the joining surface. They are called for convenience i) a fastening layer, ii) a hard-soldered layer and iii) an oxidation-resistant layer (compatible with hard solder). The attachment layer contained TiC and was applied to a significant portion of the interface area via the conventional CVD method known in the art. This gave an exposed diamond coated by and chemically bonded to the TiC layers. This layer must be thick enough to produce a strong bond (e.g., at least 0.1 micron, preferably at least 0.3 micron) and not so thick as to be exfoliated (e.g., less than about 5 microns). Then, the so-called hard-soldered layer was applied to the surface of the joint. The hard-soldered layer contained the formulation of the material selected for a good bond with the TiC-fixing layer and was distributed over the entire surface of the combination previously coated with TiC. In this example, metal tungsten was used as a hard-solder layer because of its well-known tendency to be wetted by molten hard fusion and its high melting point, which ensures that it will not be removed or deformed at an elevated temperature, which can be required for later brazing. Molybdenum is an alternative suitable material for the hard-soldered layer. The tungsten layer should be at least about 0.1 micron and less than about 20 micron, preferably between 0.5 and 2 microns thick.

[0050] Because materials typically suitable for use in a hard-soldered layer, such as tungsten and molybdenum, may be susceptible to surface oxidation at brazing temperature and may also be affected by fluxes used with hard brazes (which could reduce their ability wetting by hard fused February), a further silver-containing layer was deposited on the hard-soldered brazing layer to eliminate the effect of surface oxidation effects on the brazing ability of the hard product. PVD was used to deposit the silver layer. Alternatively, a wet chemical silver deposition technique may be used.

After the above operations have been carried out, the coated surface of the joint is brazed to another part, in this case a part made of sintered tungsten carbide, although it should be noted that steel can also be used by using any of the soldering methods.

Hardly known in the art. For example, a conventional solder paste (Arg) 49H from Johnson-Matthey) was applied to the surface of the combination of the sintered tungsten carbide portion, and then the coated surface of the diamond composite joint was brought into contact with this solder paste layer. The high frequency induction coil was used to heat the system until the solder melted, and then the solder was held in this melted state for about 10 seconds.

[0052] A "push-off" test (i.e., "similar or greater strength") was used to test the strength of the created bond. The "push-off" test means that the break is not limited to the inside of the connecting material or the interface, but includes the cracking of the material of the diamond composite or its element.

[0053] As a method for testing the strength of the ScD attachment to the cemented carbide, the plates (24 mm x 24 mm x 3 mm) of the ScD were chemically treated and coated as described above. The remaining plates were simply coated without prior chemical treatment. Carbide blocks (5 mm x 5 mm x 3 mm) had a small amount of solder paste (49H) applied on their surface (about 1 - 2 mm thick).

They were applied to the surface of the ScD plates and heated to melt the brazing alloy and thereby fix the pieces of carbide to the ScD tiles. These plates were then held in the jaws of the Instron testing machine, while the other arm repelled the carbide. Strength was measured continuously on a computer. For tiles where the etching step was not used before coating, the breaking force was very low and practically unreadable at Instron. In the case of tiles that were chemically treated according to the invention, the strength of the ScD material was less than the bond strength of the carbide to the plate, to make part of the ScD material under the carbide break away from the plate.

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