CEMENTED CARBIDE WITH HARD METAL

Abstract

A suitable cemented carbide is provided as a high-performance hard metal material for wire drawing of high tensile strength alloys. The cemented carbide comprises a relatively low binder content with the additives Cr, Ta, and / or Nb to provide high wear and corrosion resistance, high thermal conductivity, high hardness, and a desired correlation between hardness and fracture toughness.

Description

CEMENTED CARBIDE WITH HARD METAL FIELD OF INVENTION The objective herein is to describe a cemented carbide that exhibits a desired hardness-to-toughness ratio, high thermal conductivity, and excellent wear and corrosion resistance. This cemented carbide, when implemented in a specific manner, can be used as a wire drawing die for high-tensile-strength alloys. BACKGROUND OF THE INVENTION Through a combination of a soft, ductile, cobalt-based binder with a hard, wear-resistant carbide such as WC, cemented carbides exhibit exceptional properties that combine high hardness with moderate strength at temperatures up to 400 °C. Their physical and mechanical characteristics, including strength, refractoriness, thermal conductivity, resistance to compressive strain and wear, and corrosion resistance, have led to the widespread use of cemented carbides in various high-demand applications, such as cutting dies, material forming tools, structural components, mining drill bits, press molds, miniature drills for highly integrated printed circuit boards, rock drills, bearings, mechanical seals, and wear parts. Tool failures in such applications can be caused by a variety of wear mechanisms (e.g., brittle fracture, fatigue, abrasion, wear and plastic deformation, possibly assisted to varying degrees by corrosion and diffusion) that may vary according to service conditions and can occur at macroscopic and / or microscopic levels. Among metal forming processes, one application where tools experience a synergistic effect of wear and corrosion is wire drawing. During wire drawing (a cold working process), the material is pulled through a die to reduce its cross-section to the desired shape and size. Based on repeated drawing sequences and intermediate annealing, various wire shapes and sizes can be drawn. The process is a complex interaction of many parameters, and successful wire drawing involves careful selection of these parameters.These parameters can be listed as follows: wire properties (elastic limit, elastic modulus, strain hardening exponent), lubricant (coefficient of friction, viscosity), die geometry (reduction angle, length of support region, reduction area and material) and process parameters (temperature, drawing speed, material surface treatment). Steel, aluminum, and copper are the three metals most widely used to produce wire. Steel is an important constituent material for a wide range of market applications and products, such as in the automotive, construction, mining, and packaging sectors. In recent years, there has been a growing trend toward producing ultra-high-strength steel wire. Wear on wire drawing dies is a fundamental limitation in the wire drawing process. During the drawing process, friction occurs between the wire and the dies. Worn dies result in direct costs, with die replacement and reconditioning time representing an additional penalty. AAAAnn / I 7P7 / B / YILI die wear must be detected before substantial quantities of out-of-size or defective wire are produced. Cemented tungsten carbide dies have been used in wire drawing for many years. A combination of strength and wear resistance makes this material widely accepted in the steel wire industry, particularly in steel wire strand drawing. Material properties that influence the degree of wear in cemented carbide dies include hardness, thermal conductivity, microstructure and composition, lubrication or lack thereof, and specific operating conditions. Thick wire is generally dry-drawn in grades with 10 wt% or 6 wt% Co and a hardness of 1600 and 1750 Vickers, respectively. Wet drawing from 1.5–2 mm to the final dimension of 0.15–0.3 mm is usually done with drawing dies in grades with a hardness of approximately 1900–2000 HV and a Co content of less than 6.5 wt%, more often around 3–5 wt%. To reduce friction during wet drawing, an emulsion lubricant (oil in water) is sprayed onto the wire, or it is used under full immersion conditions. The process involves various pressure, temperature, and speed conditions for different contact points. The most common wear modes (which can lead to die failure during use) include fracturing, abrasive wear, stripping wear (sometimes called particle stripping), corrosion wear, and oiling. Regarding composition, alloys containing TaNbC have been shown to have the longest service life, although alloys containing VC have the finest grain size and the highest hardness. Furthermore, while nickel can be considered to improve corrosion resistance, cemented carbide grades with Co+Ni as a binder and CraCz have not exhibited adequate wire drawing properties, indicating that corrosion resistance does not directly influence wire drawing effectiveness [M. Takada, H. Matsubara and Y. Kawagishi, Wear of Cemented Carbide Dies for Steel Cord Wire Drawing, Mater. Trans., vol. 54, no. 10, pp. 2011-2017, 2017]. EP 1726672 A1 describes a cemented carbide for steel tire cord drawing comprising WC with an ultrafine grain size and between 5 and 10 wt% Co. Grain growth inhibitors include V and / or Cr to provide a Vickers HV30 hardness of approximately 1900. However, further improvement of existing cemented carbides is desired for high-demand applications (e.g., as metal wire drawing dies) with respect to wear resistance, corrosion resistance, thermal conductivity, hardness, and strength to provide the desired quality performance and extend the functional service life as long as possible. BRIEF DESCRIPTION OF THE INVENTION This description refers to a high-performance, high-hardness material suitable for physically demanding applications such as wire drawing of high-tensile-strength alloys. It also provides a material with high wear and corrosion resistance, high thermal conductivity, high hardness, and, in particular, a higher hardness-to-fracture-strength ratio. AAAAnn / I 7P7 / B / YILI The advantages of this material are partly due to its relatively low binder content and fine grain size. Furthermore, since hardness and toughness are generally mutually exclusive, an increase in the hardness-to-toughness ratio is achieved through the selective addition of additives including Cr, Ta, and / or Nb. The concentrations of these additives are controlled to ensure dissolution in the binder and, preferably, to prevent precipitation, which would otherwise be detrimental to the desired physical and mechanical characteristics of the material. Grain sizes are selectively controlled to further enhance the properties of the desired material. A cemented carbide is provided comprising: at least 93 wt% WC; Co in 3 to 5 wt%; Cr in 0.1 to 0.5 wt%; Ta and / or Nb present alone or in combination in 0.05 to 0.35 wt%; and V in 0.05 to 0.2 wt%. Preferably, the cemented carbide comprises a weight percent Cr / Co ratio in the range of 0.04 to 0.1. This configuration provides a carbide material with a relatively low binder content and a minimized Cr concentration to reduce the tendency for Cr to precipitate. This, in turn, provides a material suitable for suppressing grain growth and minimizing or eliminating the precipitation of additional phases relative to the hard phase and the binder phase. Reference within this specification to the % by weight ratio comprises a ratio of % by weight of Cr to % by weight of Co each as a respective fraction of % by weight of the total weight of the cemented carbide material. Within this specification, grain size values ​​are determined by linear intercept. To achieve ultrafine grain sizes and extremely high hardness levels (above 1900 HV30), the present material comprises grain growth inhibitor (GGI) additives. VC is one of the most effective GGIs and is generally added to hard metals requiring an ultrafine and / or fine grain size. However, the inventors have identified that VC, even below the solubility limit, partially frustrates hard metals through the precipitation of V-based phases at the WC interfaces, which in turn decreases the bond strength (holding power of the WC grain) and thus compromises the HV to KIC ratios. Consequently, the amount of VC (relative to the binder content) added to the present grades has been reduced or partially eliminated.However, to maintain high hardness and ultrafine average grain sizes, it was necessary to add other grain-refining elements (GGIs) which, although less effective than carbide in reducing grain size, still exhibit a relevant effect as grain refiners. The selected elements include Cr (i.e., in higher Cr / Co ratios relative to existing reference grades, such as commercial carbide drawing tips), Ta, and / or Nb. These elements have the advantage that they: (i) dissolve in the binder and increase the binder's strength and the work's hardenability, (ii) significantly increase corrosion resistance, and (iii) have a strong grain-refining effect that does not compromise the HV to Klc ratio. It was a goal to add these components below or around the solubility limit in the binder to avoid or minimize carbide phase precipitation. RAAAnn / I 7P7 / B / YILI additional phases (i.e., in addition to the WC and binder phases) that could compromise the material's strength and hardness. These phases tend to be hard but brittle. However, the inventors have identified that if such components are small in size (i.e., relatively smaller than the average WC grain size), the carbides are widely distributed within the microstructure, and it is suggested that they are beneficial for improving wear resistance without compromising hardness. The present cemented carbide preferably comprises two phases, including a hard phase and a binder phase. Preferably, the present material comprises exclusively two phases and is devoid of any additional phase such as a gamma phase (cubic carbide or mixed carbide phase). In particular, it is preferred that the material components added to achieve high levels of hardness and / or toughness, work hardening, high corrosion resistance, and thermal conductivity be present in solid solution within the binder and not precipitate as a separate and distinct additional phase. Accordingly, Nb, Ta, Cr, and / or V are added at respective concentrations to prevent the precipitation of a third phase within the final cemented carbide and, in particular, to prevent the presence of a mixed cubic carbide (gamma) phase. As detailed herein, Nb, Cr, Ta, and V carbides can be added as starting materials, for example, as individual carbides or mixed carbides, depending on availability from most suppliers. Such carbides and mixed carbide starting materials are generally considered suitable starting materials for the manufacture of cemented carbide based on cost and availability. As will be seen, the carbon from such carbides or mixed carbides can be present in the hard phase and, in some cases, extend the binder phase. The present cemented carbide is specifically formulated with fine grain sizes and a relatively low binder content to achieve high hardness and a desired hardness (HV) to hardness (Klc) ratio. As stated, this can be achieved, in part, by minimizing or avoiding any or high concentrations of the potent grain refiner VC, in addition to the material comprising Ta, Nb, or a combination of Ta and Nb as grain growth inhibitors, along with Cr (which also contributes to grain growth inhibition WC). Furthermore, the addition of such additives, which represent small percentages of the material by weight, has been found to positively influence the work hardening of the binder. Importantly, the amounts of Ta, Nb, and Cr are carefully controlled to ensure that these components dissolve within the metal matrix (Co) and do not precipitate.Advantageously, during any wire drawing process, plastic deformation of the binder is avoided so that there is less binder extrusion and the WC granules are better supported. The use of high speeds in the wire drawing process of high-tensile-strength wires, in order to meet increased productivity demands, has a significant effect on the heat generated due to plastic deformation and friction between the wire and the drawing tools. Most of the mechanical energy is converted into heat, resulting in temperature increases on the order of hundreds of degrees. This temperature increase greatly affects lubrication conditions, tool life, and the properties of the final product. Although the use of a suitable lubrication technique substantially reduces the amount of heat generated during drawing and, consequently, AAAAnn / I 7P7 / B / YILI reduces energy consumption; the higher the thermal conductivity of the wire drawing die material, the better it is at inducing heat dissipation and improving tool life. In order to dissipate the generated heat, it is beneficial to have a drawing tip with high thermal conductivity. Thermal conductivity increases with decreasing binder content and / or increasing grain size. However, fine or ultrafine grain sizes are required if improved hardness and wear resistance are desired. Accordingly, the grades developed herein combine relatively low binder contents (between 3 wt% and 5 wt%) and fine or ultrafine grain sizes (below 0.8 µm) to successfully combine high hardness and wear resistance, high hardness at Klc ratios, and moderate to high thermal conductivity (greater than 50 W / mK, preferably greater than 60 W / mK, preferably greater than 70 W / mK). The inventors provide a hard cemented carbide metal that is suitable, in one application, as points for drawing high-strength steel, combining a high hardness level (more than 1900 HV30, preferably more than 1950 HV30, preferably more than 2000 HV30), a moderate to high fracture toughness (Klc) level (more than 8 MPa><m1 / 2, preferentemente más de 8.3 MPa> <m1 2, preferentemente más de 8.5 mpaxm1 2), una mayor relación entre la dureza y resistencia a fractura, gran corrosión, conductividad térmica, fuertes interfaces wc aglutinante del tasas endurecimiento durante el trabajo. los grados material presente combinan las propiedades mencionadas anteriormente través un diseño microestructural que consiste en metal duro con bajo contenido aglutinante, tamaño grano ultrafino cantidad óptima cr ta o nb disuelto por debajo alrededor límite solubilidad dentro aglutinante.Optionally, the cemented carbide comprises Ta at 0.05 to 0.3 wt%; 0.1 to 0.2 wt%; 0.16 to 0.26 wt%; 0.12 to 0.16 wt% or 0.2 to 0.22 wt%. Optionally, the cemented carbide may comprise Nb at 0.05 to 0.3 wt%; 0.1 to 0.2 wt%; 0.01 to 0.07 wt%; 0.02 to 0.06 wt%; 0.01 to 0.05 wt%; 0.02 to 0.06 wt% or 0.02 to 0.04 wt%. Optionally, the cemented carbide may comprise Ta and Nb in combination at 0.05 to 0.35 wt%. 0.1 to 0.3% by weight; 0.14 to 0.28% by weight; 0.16 to 0.2% by weight; or 0.2 to 0.28% by weight. The incorporation of these components is effective in improving hardness, wear resistance, corrosion resistance, strength, and abrasion resistance. Optionally, the wt% Cr / Co ratio is in the range of 0.05 to 0.1; 0.05 to 0.09; 0.06 to 0.09; 0.06 to 0.08; 0.06 to 0.07; 0.07 to 0.1; 0.08 to 0.09. The Cr to Co ratio as described and claimed herein provides a hard metal with a low binder content, an ultrafine grain size, and the desired solubility of the grain refinement components within the binder. In particular, the precipitation of additional carbide phases (beyond the WC and binder phases) is avoided. Optionally, V is included in the range of 0.06 to 0.2% by weight; 0.08 to 0.2% by weight; 0.1 to 0.2% by weight; 0.12 to 0.18% by weight; or 0.13 to 0.17% by weight. The addition of V is advantageous for improving grain growth inhibition while minimizing any embrittlement of the material. Optionally, cemented carbide may comprise WC having a grain size in the range of 0.2 to 0.8 or 0.2 to 0.6 pm of sintered material as determined by linear intercept. RAAAnn / I 7Π7 / Β / YΙΛΙ The defined average grain sizes (particularly of the WC phases) provide the desired hardness, wear resistance, strength, and abrasion resistance. Optionally, the present cemented carbide may comprise WC in not less than 94% or 95% by weight. Optionally, the cemented carbide comprises two phases, including a hard WC phase and a binder phase; the cemented carbide further comprises Co at 3 to 5 wt%; Cr at 0.1 to 0.5 wt%; Ta and / or Nb present alone or in combination at 0.05 to 0.35 wt%; and V at 0.05 to 0.2 wt%. Preferably, WC is included as a balancing component. Optionally, the cemented carbide consists of at least 93 wt% WC; Co in 3 to 5 wt%; Cr in 0.1 to 0.5 wt%; Ta and / or Nb present alone or in combination in 0.05 to 0.35 wt%; and V in 0.05 to 0.2 wt%. Optionally, the cemented carbide may have a density in the range of 14.5 to 15.5 g / cm3; a Vickers hardness of HV30 of 1950 to 2150 or 2000 to 2100 and / or a Palmquist fracture hardness of 8 to 9.5 MPa Vm. Accordingly, the present grades comprise a high hardness-to-toughness ratio and minimized wear rates compared to existing cemented carbide grades. Optionally, a cemented carbide comprising a hard WC phase and a binder phase is provided, the cemented carbide further comprising: at least 93 wt% WC; Co in 3 to 5 wt%; Cr in 0.1 to 0.5 wt%; Ta and / or Nb present alone or in combination in 0.05 to 0.35 wt%; and V in 0.05 to 0.2 wt%. Optionally, the cemented carbide comprises WC as equilibrium wt%. Preferably, the binder phase comprises Co, Cr, Ta and / or Nb, and V. Preferably, Co, Cr, Ta and / or Nb and V are present in the Co-based binder phase in solid solution. Preferably, the present cemented carbide comprises a binder phase content of less than 5% by weight, less than 4% by weight, less than 3% by weight, or in the range of 2 to 5% by weight, 2 to 4% by weight, 2 to 3% by weight based on a total weight of the cemented carbide. Preferably, this material is free of carbon nitrides and / or carbon nitrides. Optionally, the cemented carbide may contain nitrides and / or carbonitrides as impurities. Preferably, the cemented carbide is free of Ti and Ti carbides, nitrides, and / or carbonitrides so that it is compositionally Ti-free. In one aspect, the present cemented carbide may comprise: a balance of WC; Co in 3 to 5 wt%; Cr in 0.1 to 0.5 wt%; and Ta and / or Nb; wherein the wt% Cr / Co ratio is in the range of 0.04 to 0.1. Optionally, said cemented carbide may comprise a hard WC phase and a Co-based binder phase. Preferably, said cemented carbide does not comprise a third phase such as a cubic (gamma) carbide phase. Optionally, the present material may comprise impurities including elemental, carbide, nitride, or carbonitride forms of Fe, Ti, Re, Ru, Zr, Al, and / or Y. The impurity level is a level such as less than 0.1 wt%, less than 0.05 wt%, or less than 0.01 wt% within the cemented carbide. According to a further aspect of the present invention, a wire drawing die is provided. RAARnn / I 7Π7 / Β / YILI of metallic wire comprising a cemented carbide as claimed herein. A method for manufacturing a cemented carbide article is also provided, comprising: Prepare a batch of powdered materials that includes WC at least 93% by weight, Co at 3 to 5% by weight, Cr at 0.1 to 0.5% by weight, Ta and / or Nb alone or combined at 0.05 to 0.35% by weight, and V at 0.05 to 0.2% by weight; press the batch of powdered materials to form a preform; and sinter the preform to form the article. Optionally, the powdered starting materials can be in their elemental form, carbide form, mixed carbide form, or a combination thereof. Optionally, the powdered starting materials are such that a % by weight Cr / Co ratio is in the range of 0.04 to 0.1. RAAAnn / I 7Π7 / Β / YΙΛΙ Optionally, the sintering stage may include vacuum or high-pressure processing. Alternatively, the sintering stage may include processing at a temperature in the range of 1360 to 1500°C and a pressure in the range of 0 to 20 MPa. Optionally, the article or component manufactured from this cemented carbide may be a metal wire drawing die. Alternatively, this cemented carbide may be formed as a component of a cutting die, a material forming tool, a structural component, a mining drill bit, a press mold, a miniature drill bit for highly integrated printed circuit boards, a rock drill bit, a bearing, a mechanical seal, or a wear part. Optionally, the batch of powder material may comprise WC in not less than 93.94; Co in 3 to 5% by weight; Cr3C2 in 0.1 to 0.5% by weight; and 0.05 to 0.35% by weight; 0.1 to 0.3% by weight; 0.14 to 0.28% by weight or 0.16 to 0.26% by weight of any of: i) TaC and NbC; ii) TaC without NbC or iii) NbC without TaC; and VC in 0.05 to 0.25 or 0.1 to 0.2% by weight. BRIEF DESCRIPTION OF THE FIGURES Specific modalities of the present description will now be described with reference to the various examples and accompanying drawings in which: Figure 1 is a graph of a hardness-to-toughness relationship for cemented carbide materials according to aspects of the present invention, where the dotted line corresponds to a linear correlation; Figures 2a and 2b are Figure 2b: 5000x magnification; Figures 3a and 3b are Figure 3b: 5000x magnification; Figures 4a and 4b are Figure 4b: 5000x magnification; Figures 5a and 5b are Figure 5b: 5000x magnification; Figures 6a and 6b are Figure 6b: 5000x magnification; Figures 7a and 7b are micrographs of a hard metal with hardness A; Figure 2a: 2000x magnification micrographs of a hard metal with hardness B; Figure 3a: 2000x magnification micrographs of a hard metal with hardness C; Figure 4a: 2000x magnification micrographs of a hard metal with hardness D; Figure 5a: 2000x magnification micrographs of a hard metal with hardness E; Figure 6a: 2000x magnification micrographs of a hard metal with hardness F; Figure 7a: 2000x magnification Figure 7b: 5000x magnification; Figure 8 shows SEM images of worn surfaces of various sample hardnesses according to aspects of the present invention after the sliding wear test; Figure 9 is a graph of the wear track width of various sample hardnesses after the test measured by SEM analysis; Figure 10 is a graph of thermal conductivity of sample hardness A and a reference sample hardness F. DETAILED DESCRIPTION OF THE INVENTION A high-performance cemented carbide material has been developed for the drawing of high-tensile-strength alloy wire. This material is particularly well-suited for high wear and corrosion resistance, high thermal conductivity, high hardness, and, in particular, a higher correlation between hardness and fracture toughness. These characteristics are achieved through selective control of grain size, binder content, and composition. Specifically, this cemented carbide features an ultrafine grain size, a relatively low binder content, and a correspondingly enhanced binder-wc bond strength. Examples Conventional powder metallurgy methods, including milling, pressing, forming, and sintering, were used to manufacture various sample grades of a cemented carbide according to the present invention. Specifically, cemented carbide hardnesses with weight percent compositions according to Tables 1 and 2 (elemental) were produced using known methods. Hardnesses A through G were prepared from powders forming the hard constituents and powders forming the binder phase. Each of the sample mixtures of grades A through F was prepared from powders forming the hard constituents and powders forming the binder. The following preparation method corresponds to Grade A of Table 1 below which has initial powder materials: WC 93.08 g, Cr3C2 0.30 g, Co 3.92 g, NbC 0.03 g, TaC 0.16 g, VC 0.14 g, W 0.01 g, PEG 2.25 g, Ethanol 50 mL.Those skilled in the art will appreciate that it is the relative quantities of the powdered materials that allow for proper adjustment to achieve the final powder batch and the fully sintered composition of the cemented carbides in Table 1. Accordingly, Table 1 lists the starting materials, with the exception of cobalt, in their carbide form. As will be seen, the respective carbide starting materials are used for convenience and cost-effectiveness from standard suppliers. In particular, TaC and NbC can be added as a mixed carbide starting material with their respective weight quantities indicated in Table 1. Each sample mixture was subjected to 8 h of ball milling using ethanol as the liquid medium, then oven-dried (65 °C) and sieved. The powders were uniaxially pressed at 4 Tm. The green pacts were then destemmed at 450 °C and sintered in a SinterHIP at 1450 °C (70 min) in an argon atmosphere (50 bar). PEG was added to all compositions. AAAAnn / I 7P7 / B / YILI Hardness Composition, % by weight WC NbC Co CrsC2 TaC ve A 95.35 0.05 4.00 0.30 0.15 0.15 B (comparative) 94.24 0.03 5.00 0.50 0.23 C (comparative) 96.45 0.03 3.00 0.30 0.23 D (comparative) 95.34 0.03 4.00 0.40 0.23 E (comparative) 96.55 3.30 0.15 F (comparative) 92.90 6.20 0.30 0.60 RAARnn / I 7Π7 / Β / YΙΛΙ Table 1 - Example of powder starting material compositions A to D according to aspects of the present invention and comparative grades E and F. Composition, % by weight Hardness Ta Cr V Nb W Cr / Co (Ta+Nb) / Cr (Ta+Nb) / Co Ta + Nb A 0.140 0.259 0.121 0.044 89.502 0.06499 0.711 0.046 0.184 B (comparative) 0.216 0.433 0.027 88.461 0.086657 0.559 0.048 0.243 C (comparative) 0.216 0.260 0.027 90.526 0.08666 0.932 0.081 0.242 D (comparative) 0.215 0.346 0.027 89.493 0.08665 0.698 0.060 0.242 E (comparative) 0.121 90.629 F (comparative) - 0.259 T 0.485 87.203 0.04193 - - Table 2 - details the elemental compositions and proportions of grades A to F. Characterization The various batches of powdered starting material in Table 1 were processed to produce the fully sintered final materials. Characterization of the sintered grades A to F was then carried out, including microstructural analysis using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS); hardness and toughness testing; sliding friction and wear testing; and thermal conductivity testing. The microstructure The sintered samples were mounted in Bakelite resin and polished to 1 µm before further characterization. Microstructural analysis was performed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The polished samples were etched with a Murakami etching tool to reveal the microstructure, and, according to ATM 4499-1:2010, the linear intercept technique was used to measure the WC grain size. The linear intercept method (ISO 4499-2:2008) is a method for measuring the grain size of WC. Grain size measurements are obtained from SEM images of the microstructure. For a nominally two-phase material such as a cemented carbide (hard phase and binder phase), the linear intercept technique provides information about the grain size distribution. A line is drawn through a calibrated image of the cemented carbide microstructure. When this line intercepts a WC grain, the length of the line (Zj) is measured using a calibrated ruler (where Zj = 1, 2, 3, ..., n for the first 1st, 2nd, 3rd, ..., nth grain). At least 100 grains were counted for the measurements. The mean grain size of the WC is defined as: Hardness and tenacity The Vickers indentation test was performed using 30 kgf (HV30) to assess hardness. The Palmquist fracture toughness was calculated according to: where A is a constant of 0.0028, H is the hardness (N / mm2), P is the applied load (N) and L is the sum of the crack lengths (mm) of the impressions. Friction and sliding wear test The methodology used to evaluate wear behavior was: • The sintered samples were mounted in bakelite resin and polished to 1 pm. • The samples were subsequently removed from the bakelite and placed on a circular geometry support designed for the Wazau wear tester. The Wazau wear tester on the linear reciprocating module was used in accordance with ASTM G133. 0.10 mm AI203 balls were used to characterize abrasive wear. The conditions used were: load = 150 N, speed = 250 rpm, stroke length = 10 mm, sampling frequency = 100 Hz (for a 1 h test). The samples were immersed in lubricant during the tests to simulate the actual process. • During each wear experiment, the imposed normal contact force (FN) and the concomitant tangential friction force (FT) of the pin-on-plane sliding pairs were continuously recorded. The coefficient of friction (μ) was calculated from the ratio of forces FT / FN. • After the test, the wear damage pattern was evaluated using SEM analysis and the thickness of the wear track was measured. Thermal Conductivity Specific heat and thermal diffusivity were evaluated at five different temperatures (30, 100, 200, 300, 400, and 500 °C) by the CIC Energigune technology center. Thermal conductivity was calculated from the density and thermal diffusivity measurements according to the formula: AAAAÍin / I 7Π7 / Β / ΥΙΛΙ λ(Τ) = Ρ(Τ) · Cp(T) · α(Τ) With: λ - Thermal conductivity ρ - Density (determined by pycnometry) Cp - Specific heat a - Thermal diffusivity T - Temperature To determine the specific heat (Cp), a DSC Discovery 2500 differential scanning calorimeter was used. Thermal diffusivity was quantified using the NETZSCH LFA 457 MicroFlash® laser flash device. The LFA 457 calculates thermal diffusivity using Parker's equation: l.· ti ~ 0.1388 · -----;.Ό íiCon: L = sample thickness (mm) t0.5 = time at 50% temperature increase (s) Results With reference to Tables 1 and 2, the current carbide grades combine a Co content between 3 wt% and 5 wt%, and optimal additions of VC, CrsCs, NbC, and TaC as grain growth inhibitors. Figure 1 shows the HV30 to Palmquist hardness ratios for the developed grades A to D compared to the reference grades E and F. As can be seen, the proposed materials exhibit better hardness-to-toughness ratios than the reference grades E and F. This is likely related to the replacement of VC as a grain growth inhibitor (GGI) with higher amounts of other elements (with additional benefits) such as Cr, Ta, and Nb. The HV30 and toughness values ​​are shown in Table 3. ΑΑΑΑΠη / I 7Π7 / Β / ΥΙΛΙ Composition, % by weight HV30 Klc (MPa xm°5) A 2074 8.6 B comparative 1975 9.3 C comparative 2073 8.4 D comparative 2008 8.8 E comparative 1923 8.6 F comparative 2042 8.2 Table 3 - Hardness and toughness values ​​for the current hardness A and the comparative values ​​B to F The microstructures of the reference and developed hard metal hardnesses are shown at 2000X and 5000X magnification in Figures 2a to 7b. Figures 3a and 3b are micrographs of a hard metal with hardness B at 2000X and 5000X magnification, respectively; Figures 4a and 4b are micrographs of a hard metal with hardness C at 2000X and 5000X magnification, respectively; Figures 5a and 5b are micrographs of a hard metal with hardness D at 2000X and 5000X magnification, respectively; and Figures 6a and 6b are micrographs of a hard metal with hardness E at 2000X and 5000X magnification, respectively. Figures 7a and 7b are micrographs of a hard metal with a hardness of F; Figure 7a: 2000x magnification and Figure 7b: 5000x magnification; Response to wear and tear Wear damage in terms of abrasion was assessed using Al₂O₃ balls. As can be seen in Figure 8, the wear tracks revealed that all samples underwent the same wear mechanism based on grain extraction due to the abrasive effect of the hard counterpart. Despite these similarities in the mechanism, reference sample E suffered more wear than the others due to its lower hardness. Furthermore, sample E does not contain Ta, Nb, or Cr, but only VC as a grain refiner, which was found to embrittle the material. These observations are entirely consistent with the wear track width measurements shown in Figure 9. Thermal Conductivity The thermal conductivity of standard WC / Co hard metals is approximately twice that of high-speed steel. Both thermal conductivity and thermal expansion can be tailored by changing the volume fraction of the binder phase and the grain size of the hard carbide phase. High thermal conductivity is a key property in wire drawing applications to dissipate heat along the tool and prevent premature failure due to high-temperature property degradation and thermal damage. Figure 10 compares the thermal conductivity of sample A with the reference sample F from room temperature up to 500 °C. As can be seen in Figure 10, since this property is highly sensitive to grain size, F exhibits lower thermal conductivity values.The presence of VC (a powerful grain refiner) in a higher quantity compared to Grade A makes this material less thermally conductive due to its finer grain size. In addition, the Co content in Grade F is higher than in Grade A, a fact that further contributes to its lower thermal conductivity. Unless otherwise defined, all technical and scientific terms used herein have the same meanings as would be commonly understood by an expert in the subject to which this description pertains. Unless otherwise stated, any reference to % by weight refers to the mass fraction of the component with respect to the total mass of the cemented carbide. When a range of values ​​is provided, for example, concentration ranges, percentage ranges, or ratio ranges, it is understood that each intermediate value, up to one-tenth of the unit of the lower limit, unless the context clearly indicates otherwise, falls between the upper limit and the lower limit. RAAAÍin / I 7Р7 / В / YЙЛЙ and lower limits of that interval, and any other stated or intermediate values ​​within that stated interval, are included within the subject matter described. The upper and lower limits of these smaller intervals may independently be included within the smaller intervals, and such modalities are also encompassed within the subject matter described, subject to any limits specifically excluded within the stated interval. When the stated interval includes one or both of the limits, the intervals that exclude one or both of those included limits are also included within the subject matter described. It should be understood that the terms "a" and "an" as used above and elsewhere in this document refer to one or more of the listed components. It will be clear to a person skilled in the art that the use of the singular includes the plural unless specifically stated otherwise. Therefore, the terms "a," "an," and "at least one" are used interchangeably in this application. Unless otherwise stated, all numbers expressing quantities of ingredients, properties such as size, weight, reaction conditions, and so forth used in the specification and claims shall be considered as modified in all cases by the term "approximately." Accordingly, unless otherwise stated, the numerical parameters stipulated in the following specification and appended claims are approximations that may vary depending on the desired properties sought to be obtained from the claimed material. At a minimum, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter shall at least be interpreted in light of the number of significant digits reported and by the application of ordinary rounding techniques. Throughout the application, the descriptions of various modalities use language "that comprises"; however, a person skilled in the art will understand that, in some cases, a modality may alternatively be described using language "that essentially consists of" or "that consists of". The subject matter described herein, as described herein, may be modified or varied in many ways. Such modifications and variations shall not be deemed a departure from the spirit and scope of the present matter, and it is intended that all such modifications and variations shall be included within the scope of the following claims.

Claims

1. A cemented carbide characterized in that it comprises: at least 93 wt% WC; Co in 3 to 5 wt%; Cr in 0.1 to 0.5 wt%; Ta and / or Nb present alone or combined in 0.05 to 0.35 wt%; and V in 0.05 to 0.2 wt%.

2. The cemented carbide according to claim 1, further characterized in that a weight % ratio of Cr / Co is in the range of 0.04 to 0.

1.

3. The cemented carbide according to claim 1 or 2, characterized in that it comprises Ta in 0.05 to 0.3% by weight; 0.1 to 0.2% by weight or; 0.16 to 0.26% by weight.

4. The cemented carbide according to any of the preceding claims, further characterized in that it comprises Nb in 0.01 to 0.07% by weight; 0.02 to 0.06% by weight or; 0.01 to 0.05% by weight.

5. The cemented carbide according to any of the preceding claims, further characterized in that it comprises Ta and / or Nb present alone or in combination at 0.1 to 0.3% by weight; 0.14 to 0.28% by weight; 0.14 to 0.2% by weight or; 0.2 to 0.28% by weight.

6. The cemented carbide according to any preceding claim, further characterized in that the weight % - Cr / Co ratio is in the range of 0.06 to 0.

09.

7. The cemented carbide according to any preceding claim, further characterized in that the Co is included in the range of 3 to 4.5% by weight or; 3.5 to 4.5% by weight.

8. The cemented carbide according to any of the preceding claims, further characterized in that it comprises the WC having a grain size in the range of 0.2 to 0.8 pm.

9. The cemented carbide according to claim 8, further characterized in that said range is from 0.2 to 0.6 pm.

10. Cemented carbide according to any of the preceding claims, further characterized in that it comprises WC in not less than 94% by weight or 95% by weight.

11. The cemented carbide according to claims 3, 4, 5, 6, 9 and 10, further characterized in that it comprises a density in the range of 14.5 to 15.5 g / cm3.

12. Cemented carbide according to claims 3, 4, 5, 6, 9 and 10, further characterized in that it comprises a Vickers HV30 hardness of 1950 to 2150 or 2000 to 2100.

13. The cemented carbide according to claims 3, 4, 5, 6, 9 and 10 and 12, further characterized in that it comprises a Palmquist fracture hardness of 8 to 9.5 MPa ^m.

14. A metal wire drawing die further characterized in that it comprises a cemented carbide in accordance with any preceding claim.

15. A method for manufacturing a cemented carbide article further characterized in that it comprises: preparing a batch of powder materials comprising at least 93 wt% WC, Co in 3 to 5 wt%, Cr in 0.1 to 0.5 wt%, Ta and / or Nb alone or in combination in 0.05 to 0.35 wt%, and V in 0.05 to 0.2 wt%; pressing the batch of powder materials to form a preform; and sintering the preform to form the article.

16. The method according to claim 15, further characterized in that within the batch of powder materials, a % by weight ratio of Cr / Co is in a range of 0.04 to 0.

1.

17. The method according to claim 15 or 16, further characterized in that the sintering step comprises HIP processing or a vacuum.

18. The method according to any of claims 15 to 17, further characterized in that the sintering step comprises processing at a temperature in the range of 1360 to 1520 2C at a pressure in the range of 0 to 20 MPa.

19. The method in accordance with any of claims 15 to 18, further characterized in that the article is a metal wire drawing die.

20. The method according to any of claims 15 to 19, further characterized in that the powder materials comprise: WC in not less than 93% by weight; Co in 3 to 5% by weight; CraC2 in 0.1 to 0.5% by weight; 0.05 to 0.35% by weight of any of: i) TaC and NbC; ii) TaC without NbC or iii) NbC without TaC; and VC in 0.05 to 0.25% by weight.

21. The method according to claim 20, further characterized in that the powder materials further comprise VC at 0.1 to 0.2% by weight.