RU2799380C2 - Redistribution of binder in a cemented carbide drill bit insert - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to a method for redistributing a binder in a cemented carbide insert for a drill bit, to a cemented carbide insert for a drill bit with a hardness gradient. A method for manufacturing a cemented carbide insert for a drill bit containing a WC-based hard phase component, if necessary, one or more additional solid phase components and a binder, includes the steps of: a) providing a raw cemented carbide insert for a drill bit, b) applying at least one extractor of a binder selected from a metal oxide or a metal carbonate onto the surface of said raw insert; and c) sintering the raw insert. A binder extractor, selected from a metal oxide or a metal carbonate, is applied as a liquid dispersion or slurry to a local area of the surface of the untreated cemented carbide insert in the upper part of the drill bit. After sintering the insert, it is subjected to a tumbling process in a centrifugal tumbling device for strain hardening under the following conditions: ΔHV3%≥ 9.72-0.00543×HV3_bulk,Δ HV3%=100×(HV_0.3mm-HV_bulk)/ HV _bulk, where ΔHV3 characterizes the change in Vickers hardness at a load of 3 kg after tumbling in %, HV3_bulk - Vickers hardness data at a load of 3 kg for at least 30 indentation points, measured in the central part of the cemented carbide insert for a drill bit, HV_bulk - Vickers hardness data for at least 30 indentation points, measured at the centre of the cemented carbide insert for drill bits, HV_0.3mm - Vickers hardness data for at least 30 indentation points, measured at a depth of 0.3mm below the surface after tumbling of the cemented carbide drill bit insert.

EFFECT: high wear resistance of the cemented carbide drill bit insert.

13 cl, 26 dwg, 5 tbl, 6 ex

Description

Technical field

The present invention relates to a method for redistributing binder in a cemented carbide insert for a drill bit, to a cemented carbide insert for a hardness gradient drill bit, and its use.

State of the art

Cemented carbide has a unique combination of high modulus, high hardness, high compressive strength, high wear resistance and high abrasion resistance with a good level of toughness. Therefore, cemented carbide is commonly used in products such as mining tools. In general, the hardness and toughness of cemented carbide can be varied by changing the binder content and hard phase grain size. Generally, a higher binder content increases the toughness of the cemented carbide, but decreases its hardness and wear resistance. A finer grain size of the hard phase results in a higher hardness cemented carbide that is more wear resistant, while a cemented carbide with a coarser grain size of the hard phase is not as hard but has higher impact resistance.

For maximum performance in a cemented carbide drill bit insert, a combination of these properties is required, and materials for different parts of the product have different requirements. For example, rock drilling and mineral cutting inserts should preferably have a stiffer interior to minimize the risk of failure and a harder exterior to optimize wear resistance.

WO 2010/056191 describes a method for forming a cemented carbide body containing a hard phase and a binder phase, wherein at least one region of the intermediate surface zone has a lower average binder content than the region deeper in the body.

However, there is still a need for a method that can create even higher hardness gradients, tailor the gradient to a specific application, and that can be applied even to non-symmetrical cemented carbide drill bit inserts. There is also a need for a method by which the binder phase can be redistributed, starting with a standard carbide powder that is stoichiometrically balanced in carbon content.

Brief description of the invention

Thus, the present invention relates to a method for phase redistribution of a binder in a cemented carbide insert for a drill bit containing one or more hard phase components and a binder, comprising the following steps:

a) providing a raw cemented carbide insert for a drill bit;

b) applying at least one extractor (puller) of a binder, selected from a metal oxide or a metal carbonate, to the surface of the raw cemented carbide insert for the drill bit, and

c) sintering a raw cemented carbide insert for a drill bit,

characterized in that the metal oxide or metal carbonate is applied to only at least one local area of the surface of the untreated cemented carbide insert for the drill bit.

This method allows the binder to be redistributed in the most optimal way, providing optimal functionality of the cemented carbide insert for the drill bit. For example, specific hardness profiles can be created for different applications.

Further, the present invention relates to a cemented carbide drill bit insert comprising one or more hard phase components and a binder, characterized in that there is a hardness gradient from a first surface portion to a second surface portion of a cemented carbide drill bit insert, wherein the first part of the surface is essentially opposite the second part of the surface, so that:

— the first part of the surface is 30 HV3 (Vickers hardness) softer and 80 HV3 harder than the second part of the surface, and

- the first part of the surface is 5-120 HV3 harder than the main volume, and

- the second part of the surface is 20-70 HV3 harder than the main volume.

Description of drawings

Fig. 1: Schematic representation of an insert showing the binder extractor and binder pusher applied symmetrically on opposite sides.

Fig. 2: Schematic representation of an insert showing the binder extractor and binder indenter applied asymmetrically on opposite sides.

Fig. 3: Plots of HV3 isohardness for Sample A described in Example 1.

Fig. 4: Plots of HV3 isohardness for Sample B described in Example 1.

Fig. 5: Plots of HV3 isohardness for Sample C described in Example 1.

Fig. 6: Plots of HV3 isohardness for Sample D described in Example 1.

Fig. 7: Plots of HV3 isohardness for Sample E described in Example 1.

Fig. 8: Plots of HV3 isohardness for Sample F described in Example 1.

Fig. 9: Plots of HV3 isohardness for Sample G described in Example 1.

Fig. 10: Plots of HV3 isohardness for Sample H described in Example 1.

Fig. 11: Plots of HV3 isohardness for Sample I described in Example 1.

Fig. 12: Plots of HV3 isohardness for Sample J described in Example 1.

Fig. 13: Plots of HV3 isohardness for Sample K described in Example 1.

Fig. 14: Schematic representation of an insert showing the application site of the binder extractor in Example 1.

Fig. 15: HV3 hardness profiles along the midline for samples A, B and C described in example 1.

Fig. 16: HV3 hardness profiles along the midline for samples D, E and F described in example 1.

Fig. 17: HV3 hardness profiles along the midline for samples G, H and I described in example 1.

Fig. 18: HV3 hardness profiles along the midline for samples J and K described in example 1.

Figure 19: HV5 isohardness plots for example 2, in which the binder extractor and binder ejector are applied asymmetrically.

Fig. 20: Schematic representation of the apparatus for testing with a pendulum hammer.

Fig. 21: Cobalt concentration profiles as described in example 5 for samples D and C

Fig. 22: Chromium concentration profiles as described in example 5 for samples D and G.

Fig. 23: Cr/Co concentration profiles as described in Example 5 for samples D and G.

Fig. 24: Cobalt concentration profiles as described in example 5 for sample K.

Fig. 25: Chromium concentration profiles as described in example 5 for sample K.

Fig. 26: Graph showing change in insert diameter with drilling depth for Samples C, F, and I, measured during field testing.

Detailed description of the invention

In accordance with one aspect, the present invention relates to a method for phase redistribution of a binder in a cemented carbide insert for a drill bit containing a WC solid phase, optionally one or more additional solid phase components, and a binder, comprising the following steps:

a) providing a raw cemented carbide insert for a drill bit;

b) applying at least one binder extractor, selected from a metal oxide or a metal carbonate, to the surface of the raw cemented carbide insert for the drill bit, and

c) sintering a raw cemented carbide insert for a drill bit;

characterized in that the metal oxide or metal carbonate is applied to only at least one local area of the surface of the untreated cemented carbide insert for the drill bit.

One or more additional solid phase components may be selected from TaC, TiC, TiN, TiCN, NbC, CrC. The binder phase can be selected from Co, Ni, Fe or mixtures thereof, preferably Co and/or Ni, most preferably Co. The carbide insert for the drill bit has a suitable binder content of from about 4 to about 30% by weight, preferably from about 5 to about 15% by weight. The carbide insert for the drill bit may also contain a grain refining compound in an amount of ≤20 wt%. from the content of the binder. The grain refining compound is suitably selected from the group of carbides, mixed carbides, carbonitrides or nitrides of vanadium, chromium, tantalum and niobium. The remainder of the carbide insert for the drill bit consists of one or more hard phase components.

In one embodiment of the method, the cemented carbide insert for the drill bit contains a solid phase containing at least 80% of the mass. WC, preferably at least 90% of the mass.

As used herein, the term "raw" refers to a cemented carbide drill bit insert obtained by co-grinding the hard phase component(s) and the binder and then pressing the ground powder to form a compact cemented carbide drill bit insert that has not yet been sintered. The term "binder extractor" refers to a substance which, when applied to the surface of a cemented carbide insert for a drill bit, causes the binder to migrate towards that surface during the sintering step, i.e. the binder is drawn towards the surface where the "binder extractor" is applied. The binder extractor functions by local consumption of carbon, which causes the binder to flow from areas having normal carbon levels to a local area where carbon levels are low.

It has been found that by applying a binder extractor selected from a metal oxide or metal carbonate to the surface of an untreated cemented carbide drill bit insert in at least one local area, carbon is locally consumed in that area during sintering, causing a carbon potential to be generated. This facilitates the migration of the binder phase from regions having normal or higher carbon levels to a local region which has low carbon levels. Thus, a bond-rich zone is formed in a local area of the surface of the cemented carbide insert for the drill bit. The surface of the unfinished cemented carbide bit insert on which the binder extractor is applied is referred to as the “oxide/carbonate alloyed” surface. It is well known that binder-rich zones and binder-poor zones experience tensile and compressive stresses, respectively, after sintering. It is generally undesirable to create tensile stresses. However, it has been found that high levels of compressive stress, up to a depth of at least 1 mm below the centrifugal tumbling surface, can be created after a treatment such as spin tumbling, counteracting the tensile stresses present. Thus, it is possible to benefit from the use of a binder extractor without the negative effect of tensile stresses.

The "at least one local area on the surface of the raw cemented carbide drill bit insert" can be anywhere on the surface, such as the top, bottom, or side, depending on where the increased binder content is desired. The binder extractor may be applied to one or more localized surface areas of the cemented carbide drill bit insert, depending on whether the desired effect is to provide a localized increase in toughness or wear resistance. Each "local area" may represent 0.5-85% of the total surface area of the cemented carbide insert for the drill bit, preferably 3-75%.

The sintering temperature is typically from about 1000°C to about 1700°C, preferably from about 1200°C to about 1600°C, most preferably from about 1300°C to about 1550°C. The sintering time is from about 15 minutes to about 5 hours, preferably from about 30 minutes to about 2 hours.

In one embodiment of the method, the binder extractor, which is a metal oxide or metal carbonate, is selected from Cr ₂ O ₃ , MnO, MnO ₂ , MoO ₂ , oxides of Fe, NiO, NbO ₂ , V ₂ O ₃ , MnCO ₃ , FeCO ₃ , CoCO ₃ , NiCO ₃ , CuCO ₃ or Ag ₂ CO ₃ . Alternatively, metal can also be deposited on the surface of a raw cemented carbide insert for a drill bit, which forms an oxide when heated during the sintering step. The choice of metal oxide or metal carbonate affects the properties of the cemented carbide after sintering, such as work hardening, heat resistance, and/or corrosion resistance, and the choice can be made that best suits the desired application. Metal carbonates are chosen if the corresponding metal oxide is toxic but the metal carbonate is not. In this method, there is a high degree of freedom as to where to apply the binder extractor, for example, it can be applied in or away from the wear zones of the hardmetal (carbide) tool, depending on whether the metal oxide or carbonate improves the wear resistance of the cemented carbide or not. .

In one embodiment of the method, the binder extractor is Cr ₂ O ₃ . The use of Cr ₂ O ₃ as the binder extractor has the advantage that a surface layer enriched in chromium alloy is formed which has an increased response to tumbling treatment. Consequently, higher compressive stresses are generated and the wear resistance of the cemented carbide insert for the drill bit is improved. Cr ₂ O ₃ contributes to grain refinement, and therefore, a reduced grain size is observed on the side of the insert on which Cr ₂ O ₃ is deposited.

The metal oxide or metal carbonate is suitably applied to the surface or surfaces in an amount of from about 0.1 to about 100 mg/cm ² , preferably in an amount of from about 1 to about 50 mg/cm ² . The initial mixture of cemented carbide powder should have an acceptable carbon balance of 0.95<Com/%Co<1, or have an excess of carbon that would compensate for the decrease in carbon resulting from the deposition of oxide or carbonate. The Com value is 100×S, _inset /σS, _cobalt where σS is the specific magnetic saturation, measured in Tm ³ /kg, σS, _cobalt = 2.01×10 ⁴ Tm ³ /kg. The Com value is measured with a Foerster Koerzimat CS.1097 instrument.

In one embodiment of the method, a binder extractor is applied to the top of a cemented carbide insert for a drill bit. In another embodiment of the method, a binder extractor is applied to the side of a cemented carbide insert for a drill bit. Thus, the properties of the cemented carbide insert for the drill bit can be adjusted depending on the application. With a high probability, on the surface of the cemented carbide insert for the drill bit, the place where the binder extractor is applied, which is subject to the greatest wear, is chosen.

In one embodiment, the method further comprises between steps (a) and (b) the step of applying at least one binder pusher to at least one other local area of the surface of the untreated cemented carbide insert for the drill bit. As used herein, the term "binder pusher" refers to a substance that, when applied to the surface of a cemented carbide insert for a drill bit, causes the binder to migrate away from that surface during the sintering step, i. the binder is pushed in a direction away from the surface on which the "binder pusher" is applied. The combined application of a binder extractor applied to at least one local area on the surface and a binder pusher applied to at least one other local area on the surface of a cemented carbide insert for a drill bit means that the carbon content of the untreated insert of cemented carbide for drill bit, which is in standard ranges, such as 0.95<Com/%Co<1, and using standard processes, which can improve production efficiency. Migration preferably occurs in the depth of the insert, and not along its surface.

In one embodiment of the method, the binder pusher is selected from metal carbide, carbon powder such as graphite, or mixtures thereof. When applying metal carbide, carbon powder, or a mixture thereof, a carbon gradient is created, which leads to the migration of cobalt from the surface on which it was deposited, that is, the binder is pushed from this surface of the carbide into the internal volume in this local area (areas). In the case of metal carbide, there is an additional effect of grain refinement when applied in a local area, while in the case of carbon powder, there is an effect of promoting grain growth when applied in a local area(s). The resulting difference in the grain growth gradient created is not as significant as the effect of the binder gradient on the hardness gradient.

In one embodiment, the binder pusher is a combination of metal carbide and carbon powder. The weight ratio of metal carbide to carbon powder is from about 0.05 to about 50, preferably from about 0.1 to about 25, more preferably from about 0.2 to about 15, and even more preferably from about 0.3 to about 12, and most preferably from about 0.5 to 8. The metal carbide is suitably applied to the surface or surfaces in an amount of from about 0.1 to about 100 mg/cm ² , preferably in an amount of from about 1 to about 50 mg/cm ² . The carbon powder is suitably applied to the surface or surfaces in an amount of from about 0.1 to about 100 mg/cm ² , preferably in an amount of from about 0.5 to about 50 mg/cm ² .

If only carbon powder, such as graphite, is chosen as the binder pusher, this results in coarsening of the solid phase grains in the area where it has been deposited. This will achieve a combination of high wear resistance and improved thermal conductivity in the zones on the drill bit insert exposed to the formation to be processed, and high toughness beyond these zones.

In one embodiment of the process, the metal carbide is selected from chromium, vanadium, magnesium, iron or nickel carbide, preferably chromium carbide such as Cr ₃ C ₂ , Cr ₂₃ C ₆ , Cr ₇ C ₃ .

When choosing a metal carbide such as Cr ₃ C ₂ in combination with carbon powder, there is an advantage because this combination causes the binder to migrate from the alloyed surface, and the addition of carbon prevents the grain refinement effect due to Cr ₃ C ₂ .

During sintering, any metal carbide deposited on the surface of an unfinished cemented carbide drill bit insert should substantially dissolve.

In one embodiment of the method, the binder extractor and binder pusher are applied to different local areas of the surface of the cemented carbide insert for the drill bit. Applying the binder extractor and binder pusher to different local areas creates a binder gradient between the two surfaces. Such a binder gradient means that a hardness gradient is created with a harder, binder-poor surface formed where the binder pusher has been applied, and a binder-enriched, higher toughness surface formed where the binder extractor has been applied. The combined use of the binder extractor and binder pusher on various local areas of the surface of the cemented carbide insert for the drill bit is especially useful for creating a hardness gradient in large carbide bodies where previously known methods could not create a sufficiently deep gradient. The binder extractor can be applied to one selected a surface area of the raw cemented carbide drill bit insert, and the binder pusher can be applied to another selected surface area of the raw cemented carbide drill bit insert. The binder pusher can be applied in the wear zone to reduce the binder content and therefore improve wear resistance in this area or where it is desirable to have a higher thermal conductivity. The local application of the binder extractor and binder pusher provides unique opportunities for creating carbide bodies with individual properties.

Another advantage of using this method is that self-sharpening zones can be created if the degree of wear is uneven in different areas of the surface. The contact pressure between the worn insert with a sharper end and the rock increases as the contact area decreases. In the case of a homogeneous material, wear causes the formation of a wear plane, which often requires re-sharpening using diamond grinding tools. Regrinding by grinding is costly and requires dismantling of the drill bits. Due to the inhomogeneous properties of the material, it is possible to obtain zones that wear faster and zones that wear more slowly. If the material properties of the drill bit inserts allow the wear surface to have regions of varying wear, wear planes are prevented and hence sharper wear surfaces are created compared to when homogeneous materials are used.

In one embodiment of the method, the binder extractor and binder pusher are applied to substantially opposite local areas of the surface of the cemented carbide insert for the drill bit.

In one embodiment, the method of applying the binder extractor and binder pusher is selected from pressing, dipping, painting, spraying (airbrushing), embossing, or 3D printing. Diving can be done with or without masking. The binder extractor and binder pusher can be applied to the surface of the raw cemented carbide drill bit insert as liquid dispersions or slurries. In such a case, the liquid phase is usually water, an alcohol, or a polymer such as polyethylene glycol. The concentration of the powder in the liquid phase of the suspension is usually 5-50% wt., for example, 15-40% wt. This range is preferred since the effect of the binder extractor or binder pusher is sufficiently realized. If the powder content is too high, clogging and lumping problems may occur in the liquid dispersion or slurry. Alternatively, they can be introduced as a solid, for example by adding a powder to the mold at a suitable location. The powder can be mixed with a solid state powder such as a WC-based powder. The binder extractor and binder pusher may also be applied to the cemented carbide drill bit insert in any other suitable manner. The composition and concentration of the slurry, as well as the method of its application, influence the redistribution of the binder and, therefore, allow you to control the hardness profile of the cemented carbide insert for the drill bit.

In one embodiment of the method, the binder extractor is applied to the first surface part (10) and the binder pusher is applied to the second surface part (20) in a rotationally symmetrical manner, as shown in FIG. 1.

In one embodiment of the method, the binder extractor is applied to the first surface part (10) and the binder pusher is applied to the second surface part (20) in a rotationally asymmetrical manner, as shown in FIG. 2.

Since there is flexibility in where the binder extractor and binder pusher are applied, it is possible to tailor the position of the "wear zone", ie the position on the surface having the most improved wear characteristics. For example, the wear zone may be on either the top or side of the insert, depending on where the interaction between the cemented carbide insert for the drill bit and the formation being drilled is greatest. This position varies depending on the application for which the cemented carbide insert is used for the drill bit and the position of the cemented carbide insert in the drill bit.

Cemented carbide inserts for drill bits are subjected to high compressive loads. Therefore, surface cracking, caused by small cracks growing to a critical size due to repeated periodic high loads, is a common cause of insert failure. It is known that applying a compressive stress to the surface of an insert can reduce this problem because the presence of a compressive stress can prevent crack growth and material wear. Known methods of applying compressive stress to the surfaces of a cemented carbide drill bit insert include shot peening, vibratory tumbling, and centrifugal tumbling. All of these methods rely on mechanical shock or deformation of the outer surface of the body and increase the life of the cemented carbide insert for the drill bit.

In one embodiment of the method, after the cemented carbide insert for the drill bit has been sintered, it is treated with a tumbling process. Cemented carbide drill bit inserts are subjected to a case hardening post-treatment that creates high levels of compressive stress on the inserts. For drill bit inserts, this is usually a finishing treatment, which can be centrifugal or vibratory. However, other post-treatment methods can be used to harden the surface, such as shot peening. After tumbling, there is usually an increase in the magnetic coercive force (kA/m).

A "standard" tumbling process is typically performed using a vibratory tumbling device such as a Reni Cirillo RC 650 in which 30 kg of inserts are turned at 50 Hz for about 40 minutes. An alternative typical "standard" tumbling process is the use of a centrifugal tumbling device such as the ERBA-120 with a closed lid at the top and a rotating disc at the bottom. Cooling water with antioxidants is continuously supplied at a rate of 5 liters per minute while the disk (∅600 mm) is rotating. You can also add tungsten carbide bodies to increase the load on the tumbler. The rotation causes the inserts to collide with other inserts or with any added bodies. In collision and sliding, sharp edges are removed and work hardening occurs. For "standard" tumbling using a centrifugal tumbling device, the tumbling operation is typically performed at 120 rpm for at least 20 minutes.

In one embodiment of the method, the tumbling is a "high energy tumbling" (HEG) method. To create a higher level of compressive stress in the cemented carbide insert for the drill bit, a high energy tumbling process can be used. There are many different possible process parameters that can be used to determine the WEG, including tumbler type, volume of added bodies (if any), processing time, and process parameters such as RPM for the centrifugal tumbler, etc. Thus, the most appropriate way is to define WEG as "any process that creates a certain degree of work hardening in a homogeneous cemented carbide drill bit insert composed of WC-Co and having a mass of approximately 20 g". In the present description, the WEG process is defined as a tumbling treatment that results in a change in hardness (ΔHV3%) after tumbling, measured using HV3, of at least:

Where:

HV3 _bulk is data for at least 30 indentations measured at the very center inside the cemented carbide insert for the drill bit, and HV3 _{0.3 mm} is data for at least 30 indentations averaged 0.3 mm below tumbling surfaces of the cemented carbide insert for the drill bit. This applies to measurements made on a cemented carbide drill bit insert having uniform properties. By "uniform properties" is meant that after sintering, the difference in hardness is no more than 1% from the surface zone to the bulk zone. The tumbling parameters used to achieve the work hardening described in equations (1) and (2) for a uniform cemented carbide insert for a drill bit should be applied to cemented carbide bodies having a gradient property.

с размером диска около 350 мм, вращающегося со скоростью около 200 об/мин, если операцию галтовки выполняют либо без тел, либо с телами, размер которой превышает размер подвергаемых галтовке вставок, либо со скоростью около 280 об/мин, если используемые тела меньше по размеру, чем подвергаемые галтовке вставки. Обычно вставки подвергают галтовке в течение не менее 40-60 минут. ВЭГ позволяет использовать обогащенные связующим поверхностные зоны, поскольку сжимающие напряжения, создаваемые ВЭГ, противодействуют растягивающим напряжениям, создаваемым из-за более высокого коэффициента термического расширения в зонах, обогащенных связующим, рядом с зонами, обедненными связующим.WEG tumbling can typically be performed using an ERBA 120 with a disk size of approximately 600 mm, rotating at a speed of approximately 150 rpm, if the tumbling operation is performed either without bodies, or with bodies that are larger than the size of the inserts subjected to tumbling, or at about 200 rpm, if the size of the used bodies is less than the size of the inserts subjected to tumbling; Use a tumbler

with a disk size of about 350 mm, rotating at a speed of about 200 rpm, if the tumbling operation is performed either without bodies, or with bodies that are larger than the size of the inserts subjected to tumbling, or at a speed of about 280 rpm, if the bodies used are smaller in size. size than the tumbling inserts. Usually inserts are subjected to tumbling for at least 40-60 minutes. BEG allows the use of binder-rich surface zones because the compressive stresses created by the BEG counteract the tensile stresses created due to the higher coefficient of thermal expansion in the binder-rich zones adjacent to the binder-depleted zones.

In another aspect, the present invention relates to a cemented carbide drill bit insert comprising one or more hard phase components and a binder, when there is a hardness gradient from a first surface portion to a second surface portion of a cemented carbide drill bit insert, wherein the first surface portion along essentially opposite to the second part of the surface, so that after sintering:

- the first part of the surface is 30 HV3 softer and 80 HV3 harder than the second part of the surface, and

- the first part of the surface is 5-120 HV3 harder than the main volume, and

- the second part of the surface is 20-70 HV3 harder than the main volume.

Hardness measurements are made after sintering and before any post-sintering treatment, such as tumbling.

In one embodiment, the hardness gradient is such that:

- the first part of the surface is 2% softer and +6% harder than the second part of the surface; And

- the first part of the surface is +0.5-10% harder than the main volume, and

- the second part of the surface is +0.3-6% harder than the main volume.

The first part of the surface is a surface on which a binder extractor has been applied to form an oxide/carbonate doped surface. The second part of the surface is the surface opposite to where the binder extractor is applied (the side opposite the oxide/carbonate doped surface). Optionally, the second part of the surface may be a surface on which a binder pusher has been applied to form a carbide-alloyed surface.

This is also shown in Table 1 below:

The term "major volume" here means the cemented carbide of the innermost part (center) of the drill bit insert, and in this description it is the zone having the lowest hardness.

GmbH, откалиброванного HV3 по тестовым блокам, выпущенным Euro Products Calibration Laboratory, Великобритания. Твердость измеряют в соответствии с ISO EN6507.The hardness of cemented carbide inserts is determined using Vickers hardness maps. Cemented carbide bodies are cut along the longitudinal axis and polished using standard procedures. The Vickers impressions under a load of 3 kg are then distributed symmetrically over the polished surface. Diamonds in Fig. 3-13 and 16 show the location of the HV3 prints. Hardness measurements are made with the KB30S programmable hardness tester from KB

GmbH calibrated with HV3 against test blocks issued by Euro Products Calibration Laboratory, UK. Hardness is measured in accordance with ISO EN6507.

HV3 measurements were performed as follows:

Scanning the edge of the sample.

Programming the hardness tester for imprinting at a given distance from the edge of the sample.

Indentation with a load of 3 kg along all programmed coordinates.

The computer moves the bed to each coordinate with a print and starts automatic light adjustment, auto focus and automatically measures the size of each print.

The user checks all photographs of prints for focus and other interfering factors.

The HV3 measurements for the oxide/carbonate doped surface and the side opposite the oxide/carbonate doped surface were taken from 0.3 to 0.8 mm below the surface, 10-40 prints were made, and then the average was calculated HV3 value. The measurement of HV3 for the main volume was carried out near the center of the polished surface in the place with the lowest hardness on an area of approximately 1.52 mm ² , taking the average value calculated for 15-20 prints.

In one embodiment, the maximum binder concentration (% binder-max) is less than 20% higher than the minimum binder concentration (% binder-min) in a cemented carbide drill bit insert.

In one embodiment, the minimum binder concentration (e.g., minimum Co/%Co-min) is at a depth expressed as a percentage of the total height of the sintered cemented carbide insert for the drill bit, 1-50% of the first part of the surface, preferably 5- 40%. The minimum binder concentration is usually at a depth of 0.5-10 mm, preferably 0.8-7 mm from the first part of the surface.

In one embodiment, there are two binder concentration peaks, one at the surface and the other in the main volume of the cemented carbide insert for the drill bit. There is a first maximum binder concentration (% binder-max1) (e.g. %Co-max1) on the first part of the surface (e.g. oxide/carbonate doped surface) and a second maximum binder concentration (% binder-max2) (e.g. %Co- max 2) at a depth expressed as a percentage of the total height of the cemented carbide insert for the drill bit, 15-75% of the first part of the surface (eg oxide/carbonate alloyed surface), preferably 20-65%. In one embodiment, % binder-max1 ≥ % binder-max2. In an alternative embodiment, % binder-max1 ≤ % binder-max2. % binder-max2 is usually 2-15 mm from the first part of the surface, preferably 4-12 mm. The height difference between % binder-min and % binder-max2 is usually 1.5-12 mm, preferably 2.5-10 mm.

In one embodiment, there is a first maximum concentration of chromium (%Cr-max1) on the first part of the surface (for example, on the surface doped with oxide/carbonate). In one embodiment, there is additionally a second maximum concentration of chromium (% Cr-max2) on the second part of the surface (for example, on the surface that is opposite the surface doped with oxide/carbonate), with % Cr-max1 > % Cr-max2. The minimum concentration of chromium (% Cr-min) is between % Cr-max1 and % Cr-max2 in the core volume of the cemented carbide drill bit insert. % Cr-min is preferably at a depth expressed as a percentage of the total height of the cemented carbide insert for the drill bit, 40-99%, more preferably 50-98% of the first part of the surface. The term "at the surface" is defined as a distance up to 0.3 mm from the surface.

Chemical concentrations in the cemented carbide drill bit insert are measured by wavelength dispersive spectroscopy (WDS) along the center line of the cemented carbide drill bit insert in cross section.

In another aspect, the present invention relates to the use of the cemented carbide drill bit inserts described above or below for rock drilling or oil and gas well drilling.

The following examples are illustrative, but not limiting.

Examples

Example 1 - only with applied binder extractor

Table 2 summarizes the data of the analyzed samples.

For samples AI in Table 2, the cemented carbide inserts were made using a powder mixture having a composition of 94% by weight. WC and 6% wt. Co. The grain size of the WC powder, measured as FSSS (Fischer Average Particle Size), before milling was 5 to 7 µm. WC and Co powders were ground in a ball mill under wet conditions using ethanol and with the addition of 2 wt %, polyethylene glycol (PEG 8000) as an organic binder (compacting agent) and cemented carbide grinding media. After milling, the slurry was spray-dried under N ₂ and then uniaxially pressed into drill bit inserts having an outer diameter (OD) of about 12 mm and a height of about 17-20 mm (sample B=18.7 mm in height; sample C =17.4 mm in height; sample D=18.7 mm in height; samples E and F=17.4 mm in height; samples G, H and I=20.2 mm in height) with a mass of approximately 14-17 g each, with a spherical dome ("cutting edge") on top. The cylindrical part of the insert was ground, but the dome and the lower part were left in the sintered state.

Samples A, B and C were not slurried. Samples D, E, and F are comparative examples where only the binder pusher in the form of "carbon alloyed slurry" was dipped onto the top domed surface of the cemented carbide drill bit inserts. The carbon-doped slurry consisted of 25% wt. Cr ₃ C ₂ and 5% wt. graphite dispersed in water and applied to the cemented carbide inserts so that approximately 60% of the entire length of the insert is exposed to the carbide-alloyed slurry. Samples F, G, and H are examples of the invention to which only the binder extractor was applied. Samples were treated by applying an "oxide-doped slurry" containing 30 wt. Cr ₃ O ₂ and 7% wt. PEG 300, on the domed surface of the cemented carbide insert in an amount of 0.25 to 0.28 mg/mm ² , with approximately 60% of the entire length of the insert exposed to the oxide slurry. All samples were sintered using Sinter-HIP at 5500 kPa (55 bar) Ar at 1410° C. for 1 hour. In these examples, the slurry was applied symmetrically, that is, it was applied to the domed surface an equal distance down each side of the insert.

Samples B, E, and H were tumbled using a "standard tumble" and an ERBA-120 centrifugal tumbler was used at 120 rpm for 30 minutes. Samples C, F and I were tumbled using "high energy tumble (HEG)" and used an ERBA-120 centrifugal tumbler at 170 rpm for 40 minutes.

Samples J and K are examples of the invention where cemented carbide inserts have a higher binder content. Cemented carbide inserts were made using a powder mixture having a composition of 89% wt. WC and 11% wt. Co. The grain size of the WC powder, measured as FSSS (Fischer Average Particle Size), before milling was 8 to 12 µm. WC and Co powders were ground in a ball mill under wet conditions using ethanol and with the addition of 2 wt %, polyethylene glycol (PEG 8000) as an organic binder (compacting agent) and cemented carbide grinding media. After milling, the slurry was spray dried under N ₂ and then uniaxially compressed into drill bit inserts having an outer diameter (OD) of about 17 mm and a height of about 22 mm, weighing about 31 g each with a spherical dome ("cutting edge"). ") on the top. The cylindrical part of the insert was ground, but the conical tip and the lower part were left in the same state as immediately after sintering.

Samples J and K are examples of the invention to which only the binder extractor was applied, the samples were processed by coating using the "oxide-doped slurry" dip method containing 30% of the mass. Cr ₃ O ₂ and 70% of the mass. PEG 300, covering the conical tip and the cylindrical part, in an amount of 0.25-0.35 mg/mm ² so that approximately 75% of the entire length of the insert was exposed to the oxide-doped slurry. The samples were sintered using Sinter-HIP at an AR pressure of 5500 kPa (55 bar) and a temperature of 1410° C. for 1 hour. In these examples, the slurry was applied symmetrically, that is, it was applied to the domed surface an equal distance down each side of the insert.

модели FKS 04.1 E-SA при 250 об/мин в течение 60 минут с 50 кг тел в виде карбидных шариков диаметром 7 мм.Sample K was tumbled using a "high energy tumbler (HEG)" in a centrifugal tumbler

models FKS 04.1 E-SA at 250 rpm for 60 minutes with 50 kg bodies in the form of carbide balls with a diameter of 7 mm.

In FIG. 3-13 show the HV3 isohardness curves for samples A-I, respectively, and FIG. 15-18 show the points on the centerlines for samples A-K from Table 2. The hardness profiles of the cemented carbide inserts are as described in Table 1. A binder extractor was applied to the tip (30) of the cemented carbide insert as shown in FIG. 14.

It can be seen that the hardness profiles in accordance with the present invention are very different from the hardness profiles of the prior art, and it can also be seen that there is a softer central zone in the main part and harder top and bottom parts of the cemented carbide insert for the drill bit.

Example 2 - with applied binder extractor and binder pusher

Cemented carbide inserts were prepared using the same starting material as for samples J and K (89 wt. % WC + 11 wt. % Co) and using the method described in Table 2/Example 1. Drill bit inserts were obtained by uniaxial pressing, and they had a length of 24 mm and a cylindrical base diameter of 19 mm, as well as a spherical (semi-dome-shaped) tip. Two PEG suspensions were prepared, the first "binder extractor" which consisted of 30% Cr ₂ O ₃ + PEG and the second "binder pusher" which consisted of 25% Cr ₃ C ₂ + 5% C + PEG. The suspensions were then applied to the surface of the inserts by dipping the inserts into the suspension. After that, the inserts were sintered at 1410°C and a pressure of 5000 kPa (50 bar) in an argon atmosphere. In this example, the two suspensions were applied asymmetrically on opposite sides, ie. the binder extractor was applied to the side (10) of the insert, and the binder pusher was applied to the opposite side (20) as shown in FIG. 2. The HV5 isohardness diagram is shown in FIG. 19. It can be seen that a softer core can be achieved with this method and this hardness profile has been shown to provide efficient drilling. Alternatively, the two suspensions can be applied symmetrically, as shown in FIG. 1. By adjusting the concentration and application site of the two suspensions, the phase redistribution of the binder can be adjusted to meet the needs of the application.

Example 3 - compression test of an insert

The impact strength of the drill bit inserts, samples B, C, E, F, H, and I described in Table 2/Example 1, was determined using the insert compression test (IC). The IC test method involves compressing the drill bit insert between two plane-parallel hard counter surfaces at a constant displacement rate until the insert fails. A test fixture was used in accordance with ISO 4506:2017 (E) "Hard Metals - Compression Test", with cemented carbide anvils with a hardness of more than 2000 HV, while the test method itself was adapted for testing the impact strength of inserts for drilling tip. The fixture was mounted on an Instron 5989 test frame.

The load axis coincided with the axis of symmetry of rotation of the inserts. The reaction surfaces of the fixture met the degree of parallelism required by ISO 4506:2017 (E), i.e. the maximum deflection was 0.5 µm/mm. The tested inserts were loaded by moving the traverse at a constant speed of 0.6 mm/min until failure, and the load-displacement curve was recorded. The deformability of the test bench and test fixture was subtracted from the measured load-displacement curve prior to evaluation of the test. The tests were carried out three times for inserts of each type of sample. Before each test, the reaction surfaces were checked for damage. Insert failure was considered to have occurred when the measured load suddenly dropped by at least 1000 N. Subsequent inspection of the tested inserts confirmed that in all cases this coincided with the appearance of a macroscopic visible crack. The impact strength of the material was characterized by the total absorbed strain energy before failure. The results of the compression test of the insert are shown in Table 3:

The strength of the samples measured according to the method of the present invention is higher than that of the prior art samples according to the IC test results of the comparative samples that were tumbling in the same way.

Example 4 - Pendulum Hammer

For testing with a pendulum hammer, cemented carbide inserts were made for a domed drill bit with a radius of 5.0 mm and a diameter of 10.0 mm, which were machined in the same way as samples B, C, E, F, H and I as described in Example 1. A schematic drawing of a pendulum hammer test rig is shown in FIG. 20. The inserts were rigidly fixed in the holder (30), and only their domed part protruded. On the pendulum (40), a reaction surface (50) was mounted on the head of the pendulum hammer. The counter-acting insert used was a polished (h=5.00 mm, l=19.40 mm, w=19.40 mm) fine-grained carbide insert having a Vickers hardness of approximately 1900 HV30. When the pendulum is released, the counter-surface hits the tip of the specimen. If the sample does not fail, the impact energy (E) absorbed by the sample, measured in Joules (J), is not recorded. For a given initial angle of the pendulum, the impact energy is calculated using equation 3, where m is the total mass of the pendulum hammer 4.22 kg, g is the gravitational constant 9.81 m/s ² , L is the length of the pendulum hammer 0.231 m, and α is the angle in radians.

To determine the energy required to break the sample, it is first subjected to a pendulum impact with a suitably low angle of incidence. The angle is then gradually increased in 5 degree increments until the specimen fails. After that, inserts from the same sample are subjected to a pendulum impact with an angle 3 degrees less than the angle of impact at which the destruction occurred, and the test is repeated with a gradual decrease in the angle of impact. The angle at which the insert stops breaking is recorded and the corresponding impact energy is calculated. In these tests, the reaction surface was changed every 5-10 strokes. The results are shown below in Table 4:

These results show that there is a significant increase in the impact resistance of the sample obtained using the method of the present invention, compared with samples subjected to tumbling in an equivalent way.

Example 5 - Chemical Analysis

The chemical gradient composition of the sample was examined by wavelength dispersive spectroscopy (WDS) using a Jeol JXA-8530F microprobe. Linear scanning was performed along the center line on the cross sections of the sintered materials before tumbling samples D (comparative) and G (according to the invention), as described in table 2/example 1. The samples were obtained using a precision cutter, followed by mechanical grinding and polishing. The final stage of obtaining samples was carried out by polishing with a diamond paste with a particle size of 1 μm on a soft tissue. An accelerating voltage of 15 kV was used to perform line scans with a step size of 100 µm and a probe diameter of 100 µm. Three line scans were performed for each sample and an average value was obtained. The cobalt concentration profiles are shown in FIG. 21, the chromium concentration profiles are shown in FIG. 22 and the Cr/Co concentration profiles are shown in FIG. 23.

For comparison with the cemented carbide drill bit insert having a higher binder concentration, a line scan was performed along the center line on the cross sections of the K sample after tumbling. The tumbling is not expected to affect either the chemistry or the WDS analysis. Concentration curves for Co and Cr are shown respectively in FIG. 24 and 25.

It can be seen that for samples made in accordance with the method of the present invention, the highest concentration of Co can be found in the tip and main volume of the cemented carbide insert; and the lowest Cr concentration and the lowest Cr/Co concentration are found in the main volume of the cemented carbide insert.

Example 6 - Field Test

Cemented carbide inserts C (comparative), F (comparative) and I (according to the invention) were field tested at the Sandvik test mine in Tampere, Finland, drilling granodiorite (granite with quartzite).

The drill bits were manufactured using six gauge inserts and three front inserts per bit. The diameter of the gauge pins after sintering was 10 mm and the height was 16.6 mm. The front inserts were 9 mm in diameter and 13.8 mm high. All inserts had a spherical domed tip. The test compared gauge pin wear as it is the most important part of the tip in terms of tip life. Therefore, the front inserts for all tips were made using the standard cemented carbide according to example 1, sample C, and the gauge pins were varied according to their composition in order to evaluate the effect of the composition on wear.

The tests were carried out using an HFX5 hydraulic drilling rig from Sandvik Tamrock, with a working pressure of 21000 kPa (210 bar), a feed pressure of 9000 kPa (90 bar), a rotation speed of 230 rpm and a rotation pressure of 7000 kPa (70 bar).

The diameter of the gauge pins was measured with a vernier caliper as a function of the drilling depth measured approximately every 50 m. Two C insert tips, one F insert tip, and three I insert tips were removed. A larger change in diameter indicates more wear. The change in diameter depending on the drilling depth is shown in Fig. 26, and a summary of the reduction in diameter depending on the depth of drilling is shown below in table 5:

It can be clearly seen that the number of meters drilled per 1 mm change in diameter is greater for the inserts (I) of the present invention compared to the comparative inserts (C and F), while the inserts (I) of the present invention have an increased wear resistance of 55% compared to with comparative inserts (C), and increased wear resistance by 32% compared to comparative inserts (F).

Claims (33)

1. A method of manufacturing a cemented carbide insert for a drill bit containing a WC-based solid phase component, if necessary, one or more additional solid phase components and a binder, including the following steps: a) providing a raw cemented carbide insert for the drill bit; b) applying at least one binder extractor, selected from a metal oxide or a metal carbonate, to the surface of the raw cemented carbide insert for the drill bit; and c) sintering a raw cemented carbide insert for a drill bit; characterized in that a binder extractor, selected from a metal oxide or metal carbonate, is applied as a liquid dispersion or suspension to a local area of the surface of the untreated cemented carbide insert in the upper part for the drill bit, after sintering the cemented carbide insert for the drill bit, it is subjected to a tumbling process in a centrifugal tumbling device for strain hardening under the following conditions: ΔHV3%≥9.72-0.00543×HV3 _bulk , ΔHV3%=100×(HV _0.3mm -HV _bulk )/ HV _bulk where ΔHV3 characterizes the change in Vickers hardness at a load of 3 kg after tumbling in%; HV3 _bulk - Vickers hardness data at a load of 3 kg for at least 30 indentation points, measured in the central part of the cemented carbide insert for the drill bit; HV _bulk - Vickers hardness data for at least 30 indentations measured at the center of the cemented carbide insert for the drill bit; HV _0.3mm - Vickers hardness data for at least 30 indentation points, measured 0.3mm below the surface after tumbling of the cemented carbide insert for the drill bit. 2. Method according to claim 1, characterized in that the binder extractor is Cr ₂ O ₃ . 3. The method according to claim 1 or 2, characterized in that it further comprises between stages (b) and (c) a stage in which: applying at least one binder pusher selected from metal carbide, carbon powder or a mixture thereof, in the form of a liquid dispersion or suspension, at least one other local area of the surface of the cemented carbide insert for the drill bit. 4. The method according to any one of paragraphs. 1-3, characterized in that the binder extractor and the binder pusher are applied to opposite local areas of the surface of the untreated cemented carbide insert for the drill bit. 5. The method according to any one of paragraphs. 1-4, characterized in that the binder extractor and the binder pusher are applied symmetrically. 6. The method according to any one of paragraphs. 1-4, characterized in that the binder extractor and the binder pusher are applied asymmetrically. 7. A cemented carbide insert for a drill bit containing a WC-based hard phase component, optionally one or more additional hard phase components and a binder, characterized in that it has a hardness gradient from the first surface part to the second surface part of the cemented carbide insert for drill bit, with the first part of the surface opposite the second part of the surface, so that after sintering: - the first part of the surface is 30 HV3 softer than the second part of the surface or 80 HV3 harder than the second part of the surface; And - the first part of the surface is 5-120 HV3 harder than the central part; And - the second part of the surface is 20-70 HV3 harder than the central part, wherein the minimum binder concentration (% binder-min.) in the cemented carbide insert for the drill bit is located at a depth expressed in % of the total height of the sintered insert, which is 0.5-10 mm from the first part of the surface. 8. The insert of claim 7, wherein the maximum binder concentration (% binder-max) is less than 20% higher than the minimum binder concentration (% binder-min) in the cemented carbide drill bit insert. 9. Insert according to claim 7 or 8, characterized in that the minimum binder concentration (% binder-min.) is at a depth expressed as a percentage of the total height of the sintered cemented carbide insert for the drill bit, 1-50% of the first part surfaces. 10. Insert according to any one of claims 7-9, characterized in that: - there is a first maximum concentration of binder (% binder-max. 1) on the first part of the surface, and - there is a second maximum binder concentration (% binder-max. 2) at a depth expressed as a percentage of the total height of the sintered cemented carbide insert for the drill bit, 15-75% of the first part of the surface. 11. Insert according to any one of claims 7 to 10, characterized in that there is a first maximum concentration of chromium (% Cr-max 1) on the first part of the surface. 12. Insert according to claim 11, in which there is additionally a second maximum concentration of chromium (% Cr-max. 2) on the second part of the surface, and - % Cr-max 1>% Cr-max 2, and - there is a minimum concentration of chromium (% Cr-min.), located between % Cr-max.1 and % Cr-max.2. 13. Insert according to claim 12, characterized in that % Cr-min. is located at a depth, expressed as a percentage of the total height of the sintered cemented carbide insert for the drill bit, between 40-99% of the first part of the surface.

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