CEMENTED CARBIDE FOR HIGH DEMAND APPLICATIONS

Abstract

Provided is a corrosion, erosion and wear resistant cemented carbide for high demand applications including, for example, use as a component within oil and gas production. The cemented carbide includes a hard phase and a binder phase. The cemented carbide may include, for example. Ni, Cr and Mo. The binder phase content of the cemented carbide is between 7 to 11 wt %. The WC of the cemented carbide may have an average grain size of from 0.1 to 2 μm.

Claims

1. A cemented carbide having a hard phase and a binder phase, the cemented carbide comprising: Ni present in an amount of 5.9-9.0 by wt % of the cemented carbide: Cr present in an amount of 0.45-0.75 by wt % of the cemented carbide: Mo present in an amount of 0.55-0.85 by wt % of the cemented carbide; and WC present in an amount of 85-95 by wt % of the cemented carbide, wherein the binder phase is present in an amount of 7 to 11 by wt % of the cemented carbide, and wherein the WC has a grain size of from 0.1 to 2 μm determined by linear intercept.

2. The cemented carbide of claim 1, wherein a quotient wt % f Cr/(Ni+Cr+Mo) in the cemented carbide is from 0.03 to 0.1 by wt % of the cemented carbide.

3. The cemented carbide of claim 1, wherein a quotient wt % of Mo/(Ni+Cr+Mo) in the cemented carbide is 0.04 to 0.12 by wt % of the cemented carbide.

4. The cemented carbide of claim 1, wherein the binder phase is present in an amount of 7.0 to 11.0 by wt % of the cemented carbide.

5. The cemented carbide of claim 1, wherein the WC has a grain size of from 0.2 to 1.0 μm determined by linear intercept.

6. The cemented carbide of claim 5, wherein a the WC has a grain size of from 0.4 to 0.8 μm determined by linear intercept.

7. The cemented carbide of claim 1, wherein the Ni is present in an amount of 7.0 to 8 by wt % of the cemented carbide.

8. The cemented carbide of claim 1, wherein the Cr is present in an amount of 0.55 to 0.75 by wt % of the cemented carbide.

9. The cemented carbide of claim 1, wherein the Mo is present in an amount of 0.65 to 0.8 by wt % of the cemented carbide.

10. A component selected from the group consisting of a choke valve, a control valve, a valve seat, a plug seat, a frac seat, a cage, a cage assembly, a seal ring, a component part of a valve to allow the through-flow of a fluid and a slurry, the component comprising the cemented carbide of claim 1.

11. (canceled)

12. A method of making a cemented carbide article having a hard phase and a binder phase, the method comprising: preparing a powdered batch comprising raw materials in wt % gf 6-9 Ni; 0.45-0.75 Cr; 0.55-0.85 Mo and 85-95 WC by weight of the cemented carbide article; pressing the powdered batch to form a pre-form; and sintering the pre-form to form the cemented carbide article; wherein the binder phase content of the cemented carbide article is present in an amount of from 7 to 11 by wt % of the cemented carbide article and the WC included in the powdered batch is present in an amount of 0.4 to 2 μm determined by FSSS.

13. The method of claim 12, wherein the sintering the pre-form to form the article comprises vacuum or HIP processing.

14. The method of claim 12 wherein the sintering comprises processing at a temperature 1360-1500° C. and a pressure 0-20 MPa.

15-16. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0041] A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which:

[0042] FIG. 1 is a graph of volume of material loss due to slurry erosion (mm.sup.3) for different example materials according to aspects of the present invention in addition to comparative examples;

[0043] FIG. 2 is a graph of wear induced by cavitation over time for different example materials according to aspects of the present invention in addition to comparative examples.

DETAILED DESCRIPTION

[0044] A wear resistant cemented carbide grade is provided with relative high toughness and exhibiting enhanced corrosion and erosion resistance. The inventors have identified that such physical and mechanical characteristics may be achieved via a binder phase content relative to a WC hard phase of in the range 7 to 11 wt % and in which the cemented carbide has a wt % composition 5.9-9 Ni; 0.45-0.75 Cr; 0.55-0.85 Mo and WC included as balance. The desired physical and mechanical characteristics are also achieved by controlling the grain size of WC as determined by Fisher Model 95 Sub-Sieve Sizer™ (FSSS) in the range 0.1 to 2 μm and preferably 0.2 to 1 μm. In particular, the inventors identify that the grain size of these sintered cemented carbide provides enhanced wet erosion resistance as would typically be encountered by a fluid flow control component exposed to a slurry as typically encountered within oil and gas applications.

[0045] The present cemented carbide is specifically adapted for potential high wear and high demand applications including use as a component within oil and gas production with such components being susceptible to corrosion and mechanical erosion (including in particular wet erosion). The present carbide is also suitable for the use as a tool for metal forming or as a wear part for fluid handling.

EXAMPLES

[0046] Conventional powder metallurgical methods including milling, pressing, shaping and sinter hipping were used to manufacture a cemented carbide according to the present invention. Cemented carbide materials according to the present invention were prepared in addition to comparative test coupons.

[0047] Each of the sample mixtures Grades A to G were prepared from powders forming the hard constituents and powders forming the binder. The following preparation method corresponds to Grade E of Table 1 below having starting powdered materials: WC 95.05 g, Cr3C2 0.61 g, Ni 6.89 g, C 0.07 g, Mo 0.61 g, PEG 2 g, Ethanol 50 ml. It will be appreciated by those skilled in the art that it is the relative amounts of the powdered materials that allow the skilled person and suitable adjustment is needed to make the powdered batch and achieve the final fully sintered composition of the cemented carbides of Table 1. The powders were wet milled together with lubricant and anti-flocculating agent until a homogeneous mixture was obtained and granulated by drying and sieving. The dried powder was pressed to form a green part according to the abovementioned standard shapes and sintered using SinterHIP at 1350-1500° C. and 5 MPa.

[0048] Table 1 details composition (wt %) together with additional characterisations of grades A to G in accordance with the present invention.

TABLE-US-00001 TABLE 1 Example grade material compositions A to G according to the present invention. Composition, wt % WC Raw Cr.sub.3C.sub.2/ Mo/ Total Material Binder Binder Grade WC Cr.sub.3C.sub.2 Ni Mo binder μm Tot Tot A 89.30 0.85 9.00 0.85 10.70 0.8 0.08 0.08 B 89.30 0.85 9.00 0.85 10.70 0.4 0.08 0.08 C 91.00 0.75 7.50 0.75 9.00 0.8 0.08 0.08 D 91.00 0.75 7.50 0.75 9.00 1 0.08 0.08 E 92.00 0.60 6.80 0.60 8.00 1 0.08 0.08 F 93.00 0.55 5.90 0.55 7.00 1 0.08 0.08 G 93.00 0.55 5.90 0.55 7.00 2 0.08 0.08

[0049] Hardness tests were carried out on grades A to G in accordance with ISO 3878 and toughness testing according to Palmqvist, ISO 28079. Vickers indentation test was performed using 30 kgf (HV30) to assess hardness. Palmqvist fracture toughness was calculated according to:

[00001]$K1c=A\sqrt{HV}\sqrt{\frac{P}{\Sigma L}}$

Where A is a constant of 0.0028, HV is the Vickers hardness in N/mm2, P is the applied load (N) and ΣL is the sum of crack lengths (mm) of the imprint. The results are shown in table 2.

TABLE-US-00002 TABLE 2 Hardness and toughness tests for sample grades A to G. Grade HV30 KIC A 1581 9.4 B 1622 9.3 C 1683 9.3 D 1587 9.7 E 1591 9.6 F 1664 9.5 G 1593 9.2

[0050] Table 3 details example grade D together with comparative examples 1 to 6 according to various different compositions and WC starting material particle sizes. It will be appreciated the particle size of the starting material is reduced according to standard milling and sintering procedures such that the grain size of the final fully sintered material (determined by linear intercept) may be less than (up to or approximately half) the particle size of the starting material (determined by FSSS).

[0051] The linear intercept method (ISO 4499-2:2008) is a method of measurement of WC grain size. 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 gives information of the grain-size distribution. A line is drawn across a calibrated image of the microstructure of the cemented carbide. Where this line intercepts a grain of WC, the length of the line (l.sub.i) is measured using a calibrated rule (where i=1, 2, 3, . . . n for the first 1.sup.st, 2.sup.nd, 3.sup.rd, . . . , nth grain). At least 100 grains where counted for the measurements. The average WC grain size will be defined as:

d.sub.WC=Σl.sub.i/n

TABLE-US-00003 TABLE 3 Compositions of example grade D with various comparative examples 1 to 6. WC Raw (TiC, Material, Grade WC TaC, NbC) Co Cr.sub.3C.sub.2 Ni Mo μm D 91 0 0 0.75 7.50 0.75 1 Comparative 1 90.9 0 0 0.80 8.02 0.28 5 Comparative 2 89.81 0 0 0.80 8.49 0.80 8 Comparative 3 88.6 0 0 0.90 9.60 0.9 0.8 Comparative 4 87.8 0 3.5 1.5 7 0.2 0.8 Comparative 5 94.9 0 3.3 0.6 1.1 0.1 0.8 Comparative 6 88 5 1.2 1.2 3.6 0 2

[0052] Hardness (ISO 3878), toughness (Palmqvist, ISO 28079) and TRS (ISO 3327:2009) tests were undertaken on grade D, as well as comparative examples 1 to 6. The test pieces for transverse rupture strength's determination were cylinders of Type C (cylindrical cross-section with 40×3 mm2 dimension). The samples were placed between two supports and loaded in their center until fracture occurred (3-points bending). The maximum load was recorded and averaged over minimum five samples per test. The results are shown in table 4.

TABLE-US-00004 TABLE 4 Physical and mechanical performance test results of grade D and comparative examples 1 to 6. Grade HV30 KIC TRS D 1587 9.7 4050 Comparative 1 1344 13.8 3900 Comparative 2 1210 12.2 3025 Comparative 3 1550 9.5 4550 Comparative 4 1540 10.3 3300 Comparative 5 1904 8.8 3800 Comparative 6 1934 8.7 2275

[0053] The corrosion rate of grade D and comparative examples 1, 3, 4, 5 and 6 was assessed and the results are shown in table 5. The surface roughness (Ra) of the samples was 0.036 μm. The corrosion rate in mm/year was estimated by means of mass loss against time of immersion under the following simulated test conditions: [0054] 1) Immersion for 212 h in synthetic sea water at pH 6 (3.56% wt. NaCl) at 25° C., in aerated conditions. [0055] 2) Immersion for 212 h in synthetic sea water at pH 1 (3.56% wt. NaCl+0.1M H.sub.2SO.sub.4) at 60° C., in aerated conditions.

[0056] The mass loss corrosion rate in mm/year was estimated according to the above simulated conditions using the formula (ASTM G31-72 ‘Standard Practice for Laboratory Immersion Corrosion Testing of Metals’):

Corrosion rate=8.76×10.sup.4×((weight loss (g)/(exposed surface area (cm.sup.2)×density (g/cm.sup.3)×immersion time (h))

TABLE-US-00005 TABLE 5 Corrosion immersion testing results for grades D and comparative examples 1,3, 4, 5 and 6. Material loss (mm/year) Material loss (mm/year) in synthetic seawater in synthetic seawater Grade at pH 6, and 25° C. at pH 1, and 60° C. D 0.51 × 10.sup.−3 ± 69.28 × 10.sup.−3 ± 0.14 × 10.sup.−3 0.46 × 10.sup.−3 Comparative 1 4.11 × 10.sup.−3 ± 72.31 × 10.sup.−3 ± 0.68 × 10.sup.−3 1.08 × 10.sup.−3 Comparative 3 3.46 × 10.sup.−3 ± 55.34 × 10.sup.−3 ± 0.34 × 10.sup.−3 0.96 × 10.sup.−3 Comparative 4 4.14 × 10.sup.−3 ± 105.52 × 10.sup.−3 ± 0.69 × 10.sup.−3 12.03 × 10.sup.−3 Comparative 5 1.94 × 10.sup.−3 ± 94.05 × 10.sup.−3 ± 0.96 × 10.sup.−3 3.65 × 10.sup.−3 Comparative 6 3.28 × 10.sup.−3 ± 68.31 × 10.sup.−3 ± 1.36 × 10.sup.−3 5.99 × 10.sup.−3

[0057] The corrosion resistance of grade D together with comparative example 1, 3, 4, 5 and 6 was tested by means of polarization (potentiodymamic) curves in synthetic sea water at pH 1 (3.56% wt. NaCl) at 25° C. in aerated conditions. The surface roughness (Ra) of the samples was 0.017 μm. Firstly, the open circuit potential (OCP) was recorded for 1 h, secondly the polarization resistance was estimated by applying a potential to the sample from −5 mV to +5 mV around the OCP at a scanning rate of 0.166 mV/s, finally a cyclic polarization was applied to the sample at 0.5 mV/s, from the OCP in the anodic direction to a maximum current of 5 mA/cm.sup.2, then reversed. The results are shown in Table 6.

TABLE-US-00006 TABLE 6 Corrosion resistance: OCP, breakdown or pitting potential, repassivation potential and polarization resistance of grade D and comparative examples 1, 3, 4, 5 and 6. Breakdown Repassiv- OCP or pitting ation Polar- after 1 h potential potential ization (mV/Ag/ (mV/Ag/ (mV/Ag/ resistance Grade AgCl) AgCl) AgCl) (Ω .Math. cm.sup.2) D −180 860 N/A 2051 ± 307 Comparative 1 −160 860 N/A 1743 ± 363 Comparative 3 −130 565 110 1044 ± 129 Comparative 4 −170 790 N/A 1223 ± 272 Comparative 5 −145 −90 none  809 ± 157 Comparative 6 −130 860 N/A 2687 ± 239

[0058] Wet (slurry) erosion resistance of the grades of table 3 was tested using a wet slurry erosion rig under the following conditions: [0059] 3.5% NaCl simulated sea-water slurry solution [0060] Erodent size: ˜181-250 μm [0061] slurry flow rate of ˜41 L/min; [0062] jet flow velocity of ˜24 m/s; [0063] slurry concentration of ˜2.1% wt/wt [0064] 120 minutes running time [0065] 30° angle

[0066] The results are shown in FIG. 1 which is a graph of volume of material loss during slurry erosion testing according to the above conditions. As will be noted, grade C exhibited the lowest volume loss relative to all the comparative examples tested.

[0067] The cavitation erosion resistance of grade D and comparative examples 3 to 5 were tested in 3.5% NaCl solution at 25° C. following ASTM G 32-7 (‘Standard test method for cavitation erosion using vibratory apparatus’). The results are shown in FIG. 2 which is a graph of normalized cumulative mean depth of erosion (MDE) vs time/min of exposure to the cavitation horn. As will be noted, each sample (D and examples 3 to 5) comprises two sets of results, corresponding to two separate tests of the cavitation erosion resistance as described. Grade C is represented by lines 12 and 13. Comparative 3 is represented by lines 10 and 11. Comparative 4 is represented by lines 14 and 15. Comparative 5 is represented by lines 16 and 17. As will be noted, the MDE of grade D (line 12) was the lowest of all MDE tested samples. According, the present cemented carbide material (grade D) exhibited high wear (wet erosion resistance) in combination with enhanced toughness and corrosion resistance.

[0068] Unless defined otherwise all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the presently described subject matter pertains.

[0069] Unless otherwise indicated, any reference to “wt %” refers to the mass fraction of the component relative to the total mass of the cemented carbide.

[0070] Where a range of values is provided, for example, concentration ranges, percentage range or ratio ranges, it is understood that each intervening value, to the tenth of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the described subject matter. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and such embodiments are also encompassed within the described subject matter, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the described subject matter.

[0071] It should be understood that the terms “a” and “an” as used above and elsewhere herein refer to “one or more” of the enumerated components. It will be clear to one of ordinary skill 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.

[0072] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as size, weight, reaction conditions and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present subject matter. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0073] Throughout the application, descriptions of various embodiments use “comprising” language; however, it will be understood by one of skill in the art that, in some instances, an embodiment can alternatively be described using the language “consisting essentially of” or “consisting of”.

[0074] The present subject matter being thus described, it will be apparent that the same may be modified or varied in many ways. Such modifications and variations are not to be regarded as a departure from the spirit and scope of the present subject matter, and all such modifications and variations are intended to be included within the scope of the following claims.