Method for manufacturing Anti-wear cutting tool inserts composed of cemented metal carbide by means of oxidised precursors

Abstract

The invention relates to a method for manufacturing an insert for a cermet cutting or drilling tool, according to which method (A) at least partially oxidised molybdenum powder or at least partially oxidised tungsten powder, or a mixture of at least partially oxidised molybdenum powder and at least partially oxidised tungsten powder, is added to a mould. (B) A carbon source for forming a formulation is added to the powder present in the mould. (G) Preforming is carried out by compacting the formulation. (D) A sintering heat treatment is applied to the preformed formulation until the molybdenum and / or tungsten is carburised in situ. The invention makes it possible to do away with ferrous binders while maintaining reasonable temperature and pressure conditions.

Description

[0001] Process for manufacturing cutting tool inserts and wear-resistant inserts composed of cemented metallic carbide using oxidized precursors

[0002] Scope of the invention

[0003] The present invention relates to a method for manufacturing cutting and anti-wear tool inserts composed mainly of cemented metallic carbide, particularly used in mining or oil drilling tools.

[0004] Description of the state of the art

[0005] The market for cutting tool inserts (cermet, diamond-coated, or non-diamond) is currently dominated by metal carbide materials, specifically cemented carbides. These composite materials consist of a metallic matrix, generally cobalt [Co], which is particularly toxic and harmful to the environment, or nickel [Ni], iron [Fe], or other alloys. This matrix, known as the binder phase, is reinforced by metal carbides, typically tungsten carbide [WC], and sometimes molybdenum carbide [MoC], titanium carbide [TiC], or tantalum carbide [TaC]. This hard phase typically comprises 50 to 95% of the final structure by mass. The role of the binder phase is twofold: first, to facilitate shaping and the creation of a dense and functional structure; and second, to improve the resilience and toughness that are lacking in the aforementioned hard phases.

[0006] These composite materials are manufactured using powder metallurgy, meaning that the raw materials used are in the form of powder grains generally ranging from 0.1 to 1000 µm and are shaped using various techniques such as cold compaction, plastic injection molding, or direct or indirect additive manufacturing techniques. It should be noted that most of these techniques require the incorporation of a more or less significant amount of (organic) plastic material, and sometimes a small amount of solvent, as a binder in the powder mixture.

[0007] After shaping, these materials obtain their final structure after one or more thermal (or chemical) treatment(s) whose role is to eliminate the organic compounds (binder and solvent) used to facilitate the shaping of the powder mixture (this is called debinding [100-600°C]) and to consolidate the remaining materials by melting the metallic binding phase (this is called sintering [1000-1500 °C]). Thanks to the presence of the metallic binding phase, the sintering temperatures can be maintained in an operational range (<1500°C); otherwise, the melting temperature of the hard phase (<2500°C) would require sintering temperatures that are very difficult to achieve industrially.

[0008] Thus, a typical cermet cutting insert (or cutting insert) consists, for example, of tungsten carbide [WC] and cobalt [Go] with cobalt contents of approximately 15 to 8% by mass.

[0009] In order to further optimize their wear resistance or cutting power, it is possible to add an additional diamond phase to or within these composite tools.

[0010] However, despite the industrial performance of traditional cemented carbides, the state of the art does not offer a satisfactory solution for obtaining metallic carbides, such as tungsten carbide (WC) or molybdenum carbide (MoC or Mo2C), without resorting to ferrous metallic binders such as cobalt or nickel. These elements now pose serious health and environmental concerns: cobalt is classified as a toxic and potentially carcinogenic substance, while nickel is also known for its toxicity and natural radioactivity. Furthermore, the alternative processes described in the prior art, when they attempt to eliminate these binders, generally require extreme temperature (often exceeding 1800 °C) and / or pressure (ultra-high pressure) conditions, which are difficult to reconcile with large-scale industrial implementation.

[0011] The applicant therefore deemed it necessary to propose a new manufacturing process for inserts for cermet-type cutting or drilling tools, making it possible to eliminate or replace toxic ferrous binders while maintaining equivalent, or even improved, mechanical and functional properties.

[0012] Summary of the invention

[0013] To this end, the applicant has identified the possibility of eliminating or replacing, in part or in whole, ferrous metallic binders such as cobalt or nickel.

[0014] Insert manufacturing process

[0015] The invention relates to a method for manufacturing an insert for a cermet-type cutting or drilling tool, a method according to which: Either molybdenum powder, at least partially oxidized, or tungsten powder, at least partially oxidized, or a mixture of molybdenum powder, at least partially oxidized, and tungsten powder, is introduced into a mold.

[0016] A carbon source is added to the powder present in the mold to form a formulation.

[0017] A preforming process is carried out by compacting the formulation, and

[0018] The preformed formulation is subjected to a sintering heat treatment until in situ carburization of molybdenum and / or tungsten.

[0019] The use of at least partially oxidized molybdenum and / or tungsten powders offers a significant technical advantage in the in-situ carburization process. When using pure metallic molybdenum or tungsten, the carburization reaction requires high temperatures, generally between 1400 °C and 1600 °C, and the presence of auxiliary metals to activate the reaction. However, these temperatures are incompatible with the potential presence of diamond particles in the formulation, as diamond begins to deteriorate above 700 °C. In contrast, the use of oxidized precursors, such as MoO3, and / or WO3 allows the reduction-carburization reaction to be initiated at significantly lower temperatures, typically below 1000 °C.Although a temperature of 1000°C causes some deterioration of any diamond particles present, this deterioration will still be significantly less than if they had been heated to 1400°C. This reduction of oxides to carbides is accompanied by improved reaction kinetics, facilitated by the chemical nature of the oxides and their increased reactivity with carbon. Thus, the transformation into carbides can be achieved more gently, in a more controlled manner, and without resorting to extreme temperature conditions or ferrous metallic additives. This method not only preserves the integrity of any diamond particles present in the formulation but also eliminates the need for toxic metallic binders such as cobalt or nickel, while ensuring the efficient formation of metallic carbides within the cermet matrix.

[0020] A cutting / drilling tool insert can come in various shapes depending on its application. For turning and milling tools, the insert is typically a cutting edge that can be, for example, diamond-shaped, quadrilateral, or any other shape familiar to those skilled in the art. In another example, for well drilling, the insert might be cylindrical. In all cases, the insert offers the advantage of being replaceable as it wears without having to replace the entire tool.

[0021] The insert is described as cermet-type, or cemented carbide, i.e., a metallic composite in which the matrix is ​​a metal and the reinforcement is a metallic carbide. A cermet comprises a hard phase and a binder phase. During its manufacture, the cermet also includes an organic phase composed of an organic binder and a solvent. Each phase has a very specific function, both during the manufacture and the use of the insert.

[0022] The components of the formulation, primarily in powder form, are chosen according to the desired composition of the final product, namely the presence of a carbide and a metal. According to the process of the present invention, at least one precursor is introduced which, through an in-situ chemical reaction during sintering with the carbon source, forms a carbide and preferably a metal. In other words, the process aims to obtain metallic carbides, such as molybdenum carbide and / or tungsten carbide, in the final product by in-situ carburization of the precursor(s) during sintering with the carbon source.

[0023] According to the invention, either at least partially oxidized molybdenum powder, at least partially oxidized tungsten powder, or a mixture of at least partially oxidized molybdenum and at least partially oxidized tungsten powders is introduced into the mold as a precursor. The applicant has observed, surprisingly, that the use of an oxidized metal, such as oxidized molybdenum and / or oxidized tungsten, promotes the kinetics, particularly at lower temperatures, of in-situ carburization during sintering with the carbon source. This approach makes it possible to obtain in-situ carburization of molybdenum and / or tungsten during sintering without resorting to ferrous binders such as cobalt or nickel, and without requiring extreme temperature or pressure conditions.

[0024] According to a first embodiment, to obtain molybdenum carbide in the final composition of the insert, molybdenum, at least partially oxidized, is introduced into the mold as a precursor. This can be molybdenum oxide powder, such as MoO, M0O2, and / or M0O3. Alternatively, and advantageously, the at least partially oxidized molybdenum is metallic molybdenum with a more or less thick oxide layer on its surface. In the latter case, the oxide layer on the powder grains can be formed, for example, by a thermal cycle at a moderate temperature in air. Ideally, this cycle is carried out in a range of 200°C to 300°C, allowing the formation of a dense oxide layer with acceptable and controllable kinetics. Typically, below 200°C, the generally slow kinetics do not allow for sufficient productivity.Above 300°C, the kinetics, while generally rapid, suffer from poor reproducibility and inadequate control of the oxide thickness. Controlling this oxide quantity is crucial for ensuring stoichiometric compliance of the subsequent oxide carburization.

[0025] Molybdenum, despite its numerous industrial applications, is not currently used as a primary component in cermet formulations. It is sometimes employed as an additive in very small quantities to improve the properties of certain phases, but the production of molybdenum-based metallurgical phases is not the objective. However, the properties of molybdenum and molybdenum carbide are particularly interesting.

[0026] For example, let's mention some properties of Mo2C:

[0027] Vickers microhardness of 1950 HV (close to the 2200 HV of WC)

[0028] Density of 8.20 (nearly half of the 15.7 of the WC)

[0029] Thermal conductivity of 800W / mK (8 times greater than

[0030] (ilOW / mK of WC) (2 times greater than copper and silver)

[0031] The catalytic activities of molybdenum enable reactive sintering, eliminating the need for the (excessive) use of a metallic binder phase. This is known as a "Binder Free" structure, which has the advantage of avoiding the use of cobalt, a substance criticized for its environmental and social impacts. In a second embodiment, to obtain tungsten carbide in the final composition of the insert, at least partially oxidized tungsten, such as tungsten oxide powder (WO3), is introduced into the mold as a precursor. Alternatively, and advantageously, the at least partially oxidized tungsten is metallic tungsten with a more or less thick oxide layer on its surface. In this latter case, the oxide layer on the powder grains can be formed, for example, by a thermal cycle at moderate temperature in air.Ideally, this cycle is carried out within a temperature range of 200°C to 300°C, allowing the formation of a dense oxide layer with acceptable and controllable kinetics. Typically, below 200°C, the generally slow kinetics do not allow for sufficient productivity. Above 300°C, the generally rapid kinetics suffer from poor reproducibility and poor control of the oxide thickness. Controlling this oxide quantity is important for ensuring stoichiometric compliance of the subsequent oxide carburization.

[0032] According to a third embodiment, to obtain molybdenum carbide and tungsten carbide in the final composition of the insert, a mixture of at least partially oxidized molybdenum powder and at least partially oxidized tungsten powder is introduced into the mold as a precursor.

[0033] The term "at least partially oxidized" refers to a controlled oxidation state of molybdenum and / or tungsten particles, achieved by heat treatment within a temperature range typically between 200 °C and 300 °C, preferably around 300 °C. The oxidation level is estimated from the mass gain resulting from the progressive conversion of the metal to its oxide (e.g., Mo to MoO3), this process occurring radially from the surface to the core of the particles. For example, complete oxidation of 100 g of metallic molybdenum results in approximately 150 g of MoO3. Thus, an intermediate mass gain (e.g., 105 g after 10 minutes or 115 g after 20 minutes) allows for the estimation of partial oxidation, corresponding to an oxide layer a few microns thick (e.g., for particles with a diameter of 7 µm).This partial oxidation allows the reactivity of the powders to be adjusted during sintering, without requiring complete oxidation of the entire volume of the particles.

[0034] The carbon source added to the powder in the mold can be any allotropic form of carbon, such as graphite, carbon black, carbon nanotubes (CNTs), carbon fiber, a hydrocarbon (gas or liquid), or a combination thereof. The quantity and form in which the carbon source is added to the powder are determined by the desired formulation. The purpose of the carbon source is to induce in-situ carburization of the precursors introduced as powder.

[0035] It can be advantageous to incorporate a diamond phase into the cermet composition to improve its performance. This involves introducing diamond particles into the mold to obtain a diamond insert, either homogeneously throughout its entire volume or only in a portion of it.

[0036] The particle size of the diamond particles is preferably between 0.1 and 1000 µm.

[0037] In the context of integrating molybdenum species into diamond tools, the catalytic and thermal conductivity properties of molybdenum make its incorporation at strategically chosen locations within the diamond tool (surface, interface, etc.) particularly advantageous. Thus, in the case of diamond impregnated materials, adding molybdenum to the interface between the diamonds and the cermet matrix (whether or not it contains molybdenum) can be especially beneficial, creating discrete molybdenum-containing zones around the diamond particles. The advantage of such a structure lies in the catalytic properties of molybdenum, which can promote diamond adhesion to the cermet matrix through the formation of C-Mo-A bonds, where A is a component of the cermet matrix with an affinity for molybdenum (molybdenum, tungsten, carbon, etc.). For these same reasons, it will help to limit the graphitization of the diamond.Also, due to the very good thermal conductivity of molybdenum carbide, this structure allows better heat dissipation of the cutting forces taken from the diamonds to the cermet matrix, which will result in better friction performance (cutting and wear).

[0038] When diamond particles are introduced into the powder mixture, the process preferably includes a pre-granulation step, in which the diamond particles are pre-granulated into the powder formulation.

[0039] In the specific case of diamond inserts, the diamond particles can be the carbon source or part of it; in other words, they can contribute at least partially to the carbon source. This allows for the preferential formation of carbides at the diamond-cermet interface, which provides better adhesion of the diamonds to the cermet matrix and improved resistance to diamond graphitization, notably by promoting heat exchange between the diamond and the cermet.

[0040] Optionally, the powder formulation may include copper (Ou), silver (Ag) and / or titanium (Ti) or an alloy of two or three of these elements.

[0041] Optionally, the powder mixture includes (minor) addition elements such as tantalum (Ta), rhenium (Rh), vanadium (V) or titanium (Ti).

[0042] Adding alloying elements, such as copper (Ou), silver (Ag), or titanium (Ti), to powder formulations can offer a dual advantage. First, these elements can act as catalysts for the carburization reaction, reducing the temperature required for the formation of metal carbides from molybdenum and / or tungsten oxides. Second, they promote carbon diffusion within the matrix during sintering, improving the homogeneity of the carburization and allowing the desired stoichiometry to be reached more quickly. This synergy between temperature reduction and improved diffusion helps optimize the overall process kinetics while preserving the integrity of sensitive phases such as diamond particles.

[0043] Optionally and advantageously, the powder formulation may include, preferably in a minority, metal carbides, such as molybdenum carbide and / or tungsten carbide, so as to improve the final properties of the insert.

[0044] The powders used for the hard phase and the binder phase of cermet typically include a particle size of 0.1 to 1000 µm.

[0045] In an advantageous embodiment, the mold is filled differentially, i.e., powders of distinct formulations are introduced at specific locations within the mold, so as to impart to the resulting part a structure with a locally variable composition. For example, one end of the insert may be enriched with carbide precursor elements (such as at least partially oxidized molybdenum and / or at least partially oxidized tungsten) to form an in situ carbide-reinforced zone during sintering, while the remainder of the insert may consist of a simpler composition, suitable for a secondary function such as fastening or brazing, and not requiring the same mechanical properties or wear resistance.

[0046] Compaction

[0047] Preforming the formulation by compaction can, for example, be cold compaction, which involves subjecting the mold contents to extreme isostatic pressure, preferably between 500 and 6000 bar, at ambient temperature. The pressure agents are generally fluids, such as water or oil.

[0048] It could also be hot compaction, which follows the same principles but is carried out simultaneously with the sintering heat treatment. In this case, compaction and heat treatment take place concurrently, preferably by hipping (hot isostatic pressing) or hot pressing (uniaxial hot pressing).

[0049] Preferably, preforming is carried out by uniaxial compaction in steel tooling.

[0050] Compaction offers the advantage of applying a homogeneous pressure over the entire mold.

[0051] Fjsitt ge

[0052] The heat treatment is carried out by a sintering step, preferably in the solid phase.

[0053] The addition of elements such as copper and silver can sometimes lead to very small quantities of liquid phase in order to add dissolution / precipitation phenomena to the sintering mechanisms.

[0054] Advantageously, the sintering process can be designed as a sequence of successive thermal transformations, allowing for optimized conversion of precursors into metallic carbides. This gradual approach enables better control of the reduction and carburization kinetics, while limiting thermal stress on sensitive components such as diamond particles.

[0055] Typically, sintering can be broken down into several steps

[0056] • A first phase of partial reduction of the oxides, beginning at low temperature, allows the progressive elimination of oxygen without altering the other components of the formulation. • A second, faster reduction phase initiates the introduction of carbon into the metallic structure.

[0057] • A pre-carburization phase allows the formation of intermediate carbides in a still porous matrix.

[0058] • Finally, a controlled temperature increase up to approximately 1000 °C allows for atomic redistribution and stabilization of the desired final phase.

[0059] This sequenced sintering strategy not only lowers the overall temperature of the process, but also promotes the formation of homogeneous and stable carbides, while preserving the integrity of any diamond phases and eliminating the need for ferrous metallic binders such as Cobalt or Nickel.

[0060] Deposit t_ _dj a _ c_quch_e _di_aman_t_é e_ _s_ur_ _l_'_in_s_e rt

[0061] In certain applications, for example for oil and mining drilling, it may be advantageous for the cutting surface of the insert to be coated with a diamond layer, typically by CVD deposition.

[0062] A_j_ou t_ _ 1 o_c a 1_ _de_ _mo ybdène _ _à L _ l_'_i nter f a_c e _ _e_n t r_e_ _ l_e_s _ dd lover s_ _e t_ _1 a mqt C

[0063] In a preferred embodiment of the invention, the local addition of molybdenum can be carried out at the interface between the diamonds and the cermet matrix. This addition can be achieved either by preferential granulation of a first powder mixture conforming to the descriptions of the new formulations as described above, or by chemical (e.g., electrolytic) or physical (e.g., vapor-phase physics) deposition. In this case, the diamond particles are pre-granulated with molybdenum species Mo, MoC, and MO2C by chemical or physical deposition.

[0064] The invention also relates to a cermet-type cutting or drilling tool insert obtained by the manufacturing process according to the invention, in which at least one zone comprises at least 30% by mass of molybdenum carbide and / or tungsten carbide.

[0065] Area

[0066] A zone is defined as a volume fraction of the insert. The composition of an insert is not necessarily homogeneous; it can vary depending on the intended use of the cutting or drilling tool fitted with the insert. Therefore, it is possible to divide the insert into several zones distinguished by their composition.

[0067] A zone preferably represents more than 1% of the total volume of the insert, preferably more than 2%, more than 3%, more than 4%, more than 5%, more than 6%, more than 7%, more than 8%, more than 9%, more than 10%, more than 11%, more than 12%, more than 13%, more than 14%, more than 15%, more than 20%, more than 25%, more than 30%, more than 35%, more than 40%, more than 45%, more than 50%, more than 55% or even more

[0068] An area can be continuous or a set of discrete areas, i.e. similar spaced entities distributed in an insert.

[0069] In a first embodiment, the insert comprises at least one zone containing molybdenum carbide (MoC) and / or dimolybdenum carbide (Mo2C), preferably with a mass content of between 0 and 85% MoC and a few percent Mo2C. In this way, the cermet can benefit from the advantageous properties of (di)molybdenum carbide mentioned above. This hard phase represents more than 50% of the cermet's mass content.

[0070] Optionally, the binding phase may include copper (Cu), silver (Ag) or titanium (Ti) or an alloy of two or three of these elements to catalyze the densification / sintering mechanisms.

[0071] Optionally, the insert is reinforced by the addition of (minor) alloying elements such as tungsten (W), tantalum (Ta), rhenium (Rh), vanadium (V) or titanium (Ti).

[0072] In some embodiments, the insert of the invention is cobalt-free, at least in one area.

[0073] Optionally, the organic binder and solvent together represent a maximum of a few percent of the cermet's mass content, for example, less than 10%, less than 5%, less than 4%, less than 3%, less than 2%, or less than 1%. The organic binder is typically paraffin, polypropylene, polyethylene, or other organic materials. The solvent is typically acetone, octane, ethanol, or any other solvent capable of solubilizing the organic binder(s) used. i aman t é_e

[0074] In certain applications, for example for oil and mining drilling, it may be advantageous for the cutting surface of the insert to be coated with a diamond layer.

[0075] In an advantageous embodiment, the insert comprises at least one zone at the cermet-diamond layer interface containing molybdenum species. In the fabrication of cermet inserts coated with a diamond layer, when this diamond layer is formed on the insert by CVD deposition, cobalt acts as an inhibitor. Conversely, the molybdenum on the surface of the insert acts as a catalyst and is an excellent precursor for diamond synthesis and growth. It is thus possible to benefit from the catalytic properties of molybdenum. The presence of molybdenum also improves the adhesion of the diamond layer to the cermet and limits the detrimental effects (diffusion barrier) of certain cermet species (cobalt, for example).

[0076] The resulting insert is preferably free of ferrous binders such as cobalt or nickel.

[0077] Detailed description of the invention

[0078] The invention will now be explained in more detail, with the help of the attached drawings, on which:

[0079] Figure 1 is a block diagram of a manufacturing process for a cermet-type insert according to the invention.

[0080] Figure 2 illustrates the oxidation of metallic molybdenum.

[0081] Figure 3 illustrates pregranulated diamond particles 7a and 7b from precursors produced using different techniques. Figure 4 schematically shows a cross-section of a cermet-type insert obtained by the manufacturing process according to the invention.

[0082] With reference to Figure 1, a method for manufacturing an insert for a cermet-type cutting or drilling tool, a method in which:

[0083] A: Either molybdenum powder, at least partially oxidized, or tungsten powder, at least partially oxidized, or a mixture of molybdenum powder, at least partially oxidized, and tungsten powder, is introduced into a mold.

[0084] B: A carbon source is added to the powder present in the mold to form a formulation.

[0085] 0: A preforming is carried out by compacting the formulation, and

[0086] D: The preformed formulation is subjected to a sintering heat treatment until in situ carburization of molybdenum and / or tungsten.

[0087] The introduction A of precursors into the cermet of the insert can be carried out in the form of powders of each of the precursors in question, possibly in combination with other species, during the preparation of the powder formulation.

[0088] The added carbon source that is added to the powder present in the mold can be, among other things, any allotropic form of carbon such as graphite, diamonds, soot, carbon nanotubes (CNT), carbon fiber, or a hydrocarbon (gas or liquid).

[0089] When the precursor is molybdenum, at least partially oxidized, it can be molybdenum oxide powder (M0O3) or, alternatively, metallic molybdenum powder with a more or less thick oxide layer on its surface. In the latter case, the oxide layer on the powder grains can be formed, for example, by a thermal cycle at a moderate temperature in air. Ideally, this cycle is carried out in a range of 200°C to 300°C, allowing the formation of a dense oxide layer with acceptable and controllable kinetics. Typically, below 200°C, the kinetics, which are generally slow, do not allow for sufficient productivity. Above 300°C, the kinetics, which are generally rapid, suffer from poor reproducibility and poor control of the oxide thickness. Controlling this quantity of oxide is important for ensuring the stoichiometric conformity of the subsequent oxide carburization.Figure 6 schematically illustrates the formation of the oxide layer 62 around the metallic molybdenum grains 61. The use of an oxidized precursor helps to promote the kinetics, particularly at lower temperatures, of post-carburization during sintering.

[0090] In a typical example, the molybdenum oxide used is molybdenum trioxide (MoO3). The sintering process can then be described as follows:

[0091] • Phase 1 - Partial reduction of oxides:

[0092] An initial thermal reduction of MoO3 begins at approximately 370 °C and continues up to about 630 °C. During this stage, a progressive loss of oxygen is observed, leading to the complete disappearance of MoO3, as confirmed by Raman spectroscopy. In the presence of a reducing agent such as carbon black, gases such as CO2 and CO are detected, indicating an active reduction reaction.

[0093] • Phase 2 - Rapid reduction and initiation of precarburization: A second, more abrupt reduction occurs from 800 °C and ends rapidly around 807 °C. This stage is characterized by the removal of the last oxygen atoms and the simultaneous introduction of carbon into the metallic structure.

[0094] • Phase 3 - Pre-carburization:

[0095] Within this narrow temperature range (800-807 °C), intermediate molybdenum carbides form in a disordered manner within a still porous matrix. These phases can include, according to the literature, forms such as MoC, MoCi_ x , a-MoCi-x, p-Mo2C, y-Mo2C or even Mo3C2.

[0096] • Phase 4 - Atomic redistribution and final densification:

[0097] By continuing to raise the temperature to approximately 1000 °C, the intermediate carbides gradually transform through atomic redistribution into the desired final phase, typically molybdenum carbide Mo2C. At this stage, the part becomes dense, marking the end of the sintering cycle.

[0098] Referring to Figure 7, when diamond particles are introduced into the mold, they can be pre-coated to improve their distribution within the cermet matrix. This coating may include molybdenum and / or tungsten. The coating of the diamond particles can be achieved either by preferential granulation of a first powder mixture conforming to the specifications of new formulations, or by chemical (e.g., electrolytic) or physical (e.g., vapor-phase deposition) deposition. Particle 7a illustrates a diamond particle 72 whose coating layer includes molybdenum 71.This coating obtained by (pre-)granulation gives the particle a substantially spherical shape and is typically thicker (10 to 1000 µm) than a similar coating layer obtained by chemical or physical deposition, which is typically thinner (0.1 to 10 µm) and adopts the morphology of the horn-shaped diamond 72 illustrated on particle 7b. In both cases, the cermet matrix 73 is then granulated around it, allowing almost exclusively pre-granulated diamond particles to be introduced into the mold as powder, without the need to add carbide powder. This ensures good distribution of the diamonds, which do not touch each other.

[0099] The local addition of at least partially oxidized molybdenum and / or at least partially oxidized tungsten can be carried out in a defined area of ​​the insert. This addition can be achieved either by preferential filling during the preforming of the insert or by post-deposition, either chemical (e.g., electrolytic) or physical (e.g., vapor-phase physics). With reference to Figure 4, insert 2 illustrates this embodiment where the precursors 22 and the diamond particles 23 are located in a defined area of ​​the insert 21 where the functionality of the molybdenum and / or tungsten is to be provided. Typically, this area can advantageously be close to the upper surface of the insert if the insert is to be used subsequently as a substrate for diamond synthesis. Advantageously, the upper surface of the insert can be coated with a diamond layer 24, typically obtained by CVD deposition.

[0100] Another interesting architecture could be to preferentially locate the precursors as a backup to the insert for assembly compatibility (brazing, welding) or to promote heat exchange between the insert and its support (typically the drill bit). In all cases, this embodiment is characterized by obtaining a conventional cermet zone distinct from the new formulation zone 231. The diamonds 233 can be located in one or the other (or both) zones. Typically, if the portion containing the precursors 231 is relatively thick (>500 µm) or if it contains diamonds 233 (as is the case in Figure 2c), the preferred zone will be obtained by differential filling during cold preforming.If the thickness of this part can be relatively small (interface effect only) the preferred zone can be obtained by chemical (e.g. electrolytic) or physical (e.g. vapor phase physics) deposition.

[0101] In one example according to the invention, the powder formulation comprises:

[0102] 63% by mass of metallic molybdenum with a particle size between 1 and 10 pm,

[0103] 16% by mass of molybdenum oxide with a particle size between 1 and 10 pm,

[0104] 2% by mass of carbon (lampblack) with a particle size between 0.1 and 1 µm, and

[0105] 19% by mass of carbon (diamond) with a particle size between 200 and 350 pm.

[0106] The insert obtained after compaction and sintering comprises: a binding phase composed of 100% Mo and representing approximately 34% by mass of the insert obtained, a hard phase composed by mass of 99% M02C and 1% MoC, the hard phase representing approximately 47% by mass of the insert obtained, and diamond reinforcements representing approximately 19% by mass of the insert obtained.

Claims

DEMANDS 1. A method for manufacturing an insert for a cermet-type cutting or drilling tool, a method in which: (A) Either at least partially oxidized molybdenum powder, or at least partially oxidized tungsten powder, or a mixture of at least partially oxidized molybdenum powder and at least partially oxidized tungsten powder, is introduced into a mold (B) A carbon source is added to the powder present in the mold to form a formulation, (0) The mixture of the formulation is compacted, and (D) The compacted formulation is subjected to a sintering heat treatment until in situ carburization of molybdenum and / or tungsten.

2. A manufacturing process according to claim 1, wherein molybdenum oxide powder such as MoO, M0O2 and M0O3 is introduced into the mold as partially or totally oxidized molybdenum powder.

3. Manufacturing process according to claim 1, wherein metallic molybdenum powder having a surface oxide layer formed by a thermal cycle at a temperature in a range of 200°C to 300°C under air is introduced into the mold as partially or totally oxidized molybdenum powder.

4. A manufacturing process according to any one of the preceding claims, wherein a carbon source of any allotropic form of carbon, such as, for example, is added to the powder present in the mold as a carbon source. graphite, soot, carbon nanotubes, carbon fiber, a hydrocarbon or a combination thereof.

5. A manufacturing process according to any one of the preceding claims, wherein diamond particles are added to the powder present in the mold.

6. A manufacturing process according to claim 5, wherein the diamond particles contribute at least partially to the carbon source.

7. Manufacturing process according to claim 5 or 6, wherein the diamond particles are pre-granulated in the formulation.

8. A manufacturing method according to any one of the preceding claims, wherein at least one face of the insert obtained is coated with a diamond layer, typically by CVD deposition.

9. A manufacturing process according to any one of the preceding claims, wherein the compaction and the sintering heat treatment take place simultaneously, preferably by hot isostatic pressing or hot uniaxial pressing.

10. A manufacturing process according to any one of the preceding claims, wherein the powder mixture comprises molybdenum carbide powder and / or tungsten carbide powder.

11. A manufacturing method according to any one of the claims previous, wherein the powder mixture comprises copper (Cu), silver (Ag) and / or titanium (Ti) or an alloy of two or three of these elements.

12. Cermet-type cutting or drilling tool insert obtained by the manufacturing process according to any one of claims 1 to 11, wherein at least one zone comprises at least 30% by mass of molybdenum carbide and / or tungsten carbide.

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