Aqueous slurry for making a powder of hard material

Abstract

An aqueous slurry that is useful upon being spray dried for the formation of a powder of hard material. The aqueous slurry includes starting powder components of the hard material. The slurry further includes an oxidation inhibitor, a surfactant in an amount between about 0.05 weight percent and about 0.30 weight percent of the weight of the starting powder components of the hard material, a binder, a defoamer and water in an between about 15 weight percent and about 30 weight percent of the weight of the weight of the starting powder components of the hard material. The aqueous slurry has a percent solids value that is between about 70 percent and about 85 percent.

Claims

1. A powder of hard material produced by the process comprising the steps of: spray drying an aqueous slurry comprising: starting powder components of the hard material; an oxidation inhibitor in an amount of about 0.2 weight percent to about 0.5 weight percent based on weight of the starting powder components of the hard material; a surfactant in an amount of about 0.05 weight percent to about 0.30 weight percent of the weight of the starting powder components of the hard material; a binder in an amount of about 1.2 weight percent to about 4.0 weight percent of the weight of the starting powder components of the hard material; a defoamer in an amount of about 0.05 weight percent to about 0.35 weight percent of the weight of the starting powder components of the hard material; and water in an amount of about 15 weight percent to about 30 weight percent of the weight of the starting powder components of the hard material; and the aqueous slurry having a percent solids of about 70 percent to about 85 percent wherein the percent solids comprises a quotient in percent of the weight of the starting powder components of the hard material divided by the sum of the weight of the starting powder components of the hard material and the weight of the water; wherein granule size distribution of the powder of hard material is D.sub.10-67.8 microns, D.sub.50-115.8 microns and D.sub.90-169.9 microns.

2. The powder of hard material of claim 1, wherein spray drying parameters comprise: an inlet temperature of about 370 C. to about 400 C., an outlet temperature of about 90 C. to about 120 C., a nozzle size of about 0.5 mm to about 3 mm, a nozzle pressure of about 10 bar to about 20 bar, and a chamber pressure of about 5 millibar of about 7 millibar.

3. The powder of hard material of claim 1, wherein the surfactant comprises polyoxyethylene (5) soyaalkylamine.

4. The powder of hard material of claim 3, wherein the polyoxyethylene (5) soyaalkylamine is present in an amount of about 0.075 weight percent to about 0.25 weight percent of the starting powder components of the hard material.

5. The powder of hard material of claim 3, wherein the polyoxyethylene (5) soyaalkylamine is present in an amount of about 0.15 weight percent of the starting powder components of the hard material.

6. The powder of hard material of claim 1, wherein the powder of hard material exhibits a pressing pressure (1.2 DF) that is less than or equal to 11.0 TSI.

7. The powder of hard material of claim 1, wherein the starting powder components comprise a hard metal powder comprising one or more powders of carbides, nitrides and carbonitrides of Group IVB, Group VB and Group VIB transition metals of the Periodic Table and binder metals comprising cobalt, nickel, iron, ruthenium, manganese, silicon, aluminum and copper and their alloys.

8. The powder of hard material of claim 7 wherein the starting powder components of the hard material comprises tungsten carbide powder and cobalt powder, the tungsten carbide powder being present in an amount greater than 50 weight percent of the starting powder components of the hard material, and the cobalt powder being present in up to 50 weight percent of the starting powder components of the hard material.

9. The powder of hard material of claim 8 wherein the tungsten carbide powder is present in an amount of about 90 weight to about 96 weight percent of the starting powder components of the hard material and the cobalt powder is present in an amount of about 4 weight percent to about 10 weight percent of the starting powder components of the hard material.

10. The powder of hard material of claim 1, wherein the binder comprises a wax dispersion.

11. The powder of hard material of claim 1, wherein the defoamer comprises alkylpolyalkyleneglycoether.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The following is a brief description of the drawings that form a part of this patent application:

(2) FIG. 1 is a graph that reports the average granule size in microns for powder batches (i.e., powder of hard material);

(3) FIG. 2 is a bar chart that reports the counts of pores (that have a size greater than 25 microns per unit area) in sintered articles made from powder batches (i.e., powder of hard material) with different media:powder ratio;

(4) FIG. 3 is a graph that reports the count of pores (that have a size greater than 25 microns per unit area) in sintered article made from powder batches (i.e., powder of hard material) with different mill additives (i.e., inhibitors and surfactant);

(5) FIG. 4 is a bar chart reports the pressing pressure for powder batches (i.e., powder of hard material) with and without Ethomeen surfactant;

(6) FIG. 5 is a bar chart that reports the milling time (in hours) for powder batches (i.e., powder of hard material) with different media:powder ratio;

(7) FIG. 6 is a bar chart that shows the iron contamination (Fe %) for powder batches (i.e., powder of hard material) with different media:powder ratio; and

(8) FIG. 7 is a chart that provides a summary of benefits.

DETAILED DESCRIPTION

(9) The present invention pertains to an aqueous slurry for making a powder of hard material (e.g., hard carbide and metallic binder). More specifically, the present invention pertains to an aqueous slurry for making a powder of hard material such as, for example, a cemented (cobalt) tungsten carbide, and the powder of hard material, as well as the article made there from. The powder of hard material and the article made there from each possess properties that essentially meet properties of a powder of hard material formed from a solvent-based hard material slurry, as well as the articles made there from, respectively.

(10) In reference to the process to make the powder of hard material, a written description of the steps is set forth below. This process has application to produce powder grades of a variety of specific compositions of powders of hard material. These compositions include powder components that can comprise one or more powders of carbides, nitrides and carbonitrides of the Tungsten, Chromium, Vanadium, Tantalum, Titanium, Molybdenum, Zirconium and Niobium with binder metals comprising one or more of Cobalt, Iron, Nickel, Ruthenium, Aluminum, Manganese, Silicon and Copper and their alloys. For the specific ingredients mentioned herein, the specific powder grade that results from this process is a cemented (cobalt) tungsten carbide powder that is of a composition of between about 93 weight percent and about 94 weight percent tungsten carbide and between about 6 weight percent and about 7 weight percent cobalt.

(11) The initial step comprises adding deionized water (DI Water) and milling media and alkylpolyalkyleneglycolether, which in this specific embodiment is available under the name Contraspum K1012 from Zschimmer & Schwarz GmbH & Co. KG in Langstein, GERMANY to a steel-lined ball mill, and then stirring this mixture in the steel-lined ball mill for about 1 minute. The content of the alkylpolyalkyleneglycolether is in weight percent of the total powder components. More specifically, in an embodiment where the powder batch is tungsten carbide and cobalt and the alkylpolyalkyleneglycolether is 0.2 weight percent, 5000 grams of tungsten carbide and cobalt powder would generate a 10 grams addition of the alkylpolyalkyleneglycolether. In this specific embodiment, the media comprises 5 millimeter (mm) cycloids that comprise a cemented (cobalt) tungsten carbide that is of a composition that comprises about 94 weight percent tungsten carbide and about 6 weight percent cobalt. As one skilled in the art can appreciate, the actual amounts of the components, as well as the media:powder ratio (i.e., the quotient of the weight of the media (e.g., cemented (cobalt) tungsten carbide cycloids) divided by the total weight of the powder components), will vary depending upon the specific powder grade and powder batch size to be produced by the process.

(12) The second step comprises adding a mixture of amines and vinyl polymers in an aqueous solution to the post-stirred mixture of the first step that is in the steel-lined ball mill. In this specific embodiment, the mixture of aqueous amines and vinyl polymers is available under the name Product KM1508 from Zschimmer & Schwarz GmbH & Co. KG in Langstein, GERMANY, which according to the product brochure is an oxidation inhibitor for aqueous preparation of hard metals. The content of the mixture of the aqueous amines and vinyl polymers (or the volume of aqueous amines as referred to below when using METAMAX I-15) as based on 100 percent active matter content is in weight percent of the total powder components. After adding the mixture of amines and vinyl polymers in an aqueous solution to form a new mixture, the new mixture is then stirred in the steel-lined ball mill for about 1 minute.

(13) Still referring to the second step, there should be an appreciation that a volume of aqueous amines can be an alternative for the mixture of amines and vinyl polymers in an aqueous solution. These aqueous amines are available under the name METAMAX I-15 from Zschimmer & Schwarz GmbH & Co. KG in Langstein, GERMANY, which according to the product brochure is an oxidation inhibitor for aqueous preparation of hard metals. Further, there is the contemplation that mixture of amines and vinyl polymers in an aqueous solution (e.g., Product KM1508) and the volume of aqueous amines (e.g., METAMAX I-15) can be used together. Table A below sets forth some of the properties of Product KM1508 and METAMAX I-15 as taken from the product brochures.

(14) TABLE-US-00002 TABLE A Properties of Product KM1508 and METAMAX I-15 Material/Property Product KM1508 METAMAX I-15 appearance clear, slightly yellowish, clear-turbid, colourless viscous liquid liquid solubility in water soluble in any proportion unrestrictedly soluble density approx. 1.07 g/cm.sup.3 approx. 1.05 g/cm.sup.3 water content not reported approx. 88% active matter approx. 28% not reported

(15) The third step comprises adding a wax dispersant to the post-stirred mixture of the second step in the steel-lined ball mill, and then stirring (or ball milling) the new mixture in the steel-lined ball mill for a pre-selected time depending upon the powder batch size and the powder grade. The content of the wax dispersant is in weight percent of the total powder components. In this specific embodiment, the wax dispersant is available under the name METAMAX B-4 from Zschimmer & Schwarz GmbH & Co. KG in Langstein, GERMANY, which according to the product brochure is a wax dispersion useful as a binding and pressing agent. Table B below sets forth some of the properties of METAMAX B-4 as taken from the product brochures.

(16) TABLE-US-00003 TABLE B Properties of METAMAX B-4 Material/Property METAMAX B-4 appearance white liquid active matter approx. 55% solubility water-miscible pH (10%) approx. 6 viscosity (20 C.) approx. 400 mPas

(17) The fourth step comprises adding the powder components to the post-stirred mixture of the third step, and then stirring (or ball milling) the new mixture in the steel-lined ball mill for a pre-selected time dependent upon the powder batch size and the powder grade. In this specific embodiment, for WCCo grade, the powders comprise only the tungsten carbide powder and the cobalt powder. The particle size of the starting powders (e.g., tungsten carbide powder and cobalt powder) can range between submicron (less than 1 micron) to about 50 microns. There should be an appreciation that the basic process is applicable to produce powder grades that comprise of one or more of carbides, nitrides, carbonitrides of Tungsten, Chromium, Vanadium, Titanium, Zirconium, Molybdenum, Tantalum and Niobium and binder metals comprising one or more of Cobalt, Iron, Nickel, Ruthenium, Aluminum, Manganese, Silicon and Copper and their alloys.

(18) The fifth step comprises adding polyoxyethylene (5) soyaalkylamines, which has application as a surfactant, to the post-ball milled mixture of the fourth step in the steel-lined ball mill. In this specific embodiment, the polyoxyethylene (5) soyaalkylamine is available under the name Ethomeen from ZZ Amsterdam, The Netherlands. Table C below sets forth some properties of the Ethomeen S/15 product.

(19) TABLE-US-00004 TABLE C Properties of Ethomeen S/15 Limits Amine number 113-119 Equivalent Mass 470-495 Gardner 0-10 Moisture 1% max Primary + Secondary Amine 2% max Chemical and physical data Typical values Appearance Liquid @25 C. Cloud point 8 C. Flash point >150 C. HLB value 11.1 Davies Scale 0-40 Initial Boiling Point C. >300(760) C. (@mm Hg) (@mm Hg) Melting point 6 C. Pour point 7 C. Specific Gravity 0.952(25) Specific Heat BTU/Lb/F. 0.470(77), 0.474(122) BTU/Lb/F. Surface Tension dynes/cm 33(0.1), 33(1.0) dynes/cm (% solution) (% solution) Vapor Pressure mm Hg @20 C. <1 mm Hg @20 C.
The content of the polyoxyethylene (5) soyaalkylamine (e.g., Ethomeen) is in weight percent of the total powder components. There is the contemplation that the content of the polyoxyethylene (5) soyaalkylamine (e.g., Ethomeen) can vary from 0 weight percent to about 0.25 weight percent of the total starting powder components. As another range, the content of the polyoxyethylene (5) soyaalkylamine can range between about 0.05 weight percent about 0.20 weight percent of the total starting powder components. Ethomeen is available in a number of different grades and there is the contemplation that each one of the grades of Ethomeen will function in a satisfactory fashion.

(20) After adding the polyoxyethylene (5) soyaalkylamines, which typically takes place between about 15 minutes to about 30 minutes before the slurry is ready for discharge from the ball mill, the mixture is and then stirred (or ball milling) in the steel-lined ball mill for a pre-selected time dependent upon the powder batch size and the powder grade. The result is the production of an aqueous slurry.

(21) The sixth step comprises discharging the aqueous slurry after the milling per the fifth step into a metal container. The seventh step is to sieve the discharged mixture of the sixth step through about 200 mesh screen. The eighth step comprises transferring the sieved slurry of the seventh step to a feed tank.

(22) The ninth step comprises adding DI (deionized) water to the ball mill to recover additional powder, and then spray drying the slurry to achieve a dry powder with specific properties. Ranges for the spray drying parameters are as follows:

(23) Inlet temperature: about 370 C. to about 400 C.

(24) Outlet temperature: about 90 C. to about 120 C.

(25) Nozzle Size: about 0.5 to about 3 millimeter

(26) Nozzle Pressure: about 10 to about 20 bar

(27) Chamber Pressure: about 5 to about 7 mbar.

(28) Specific parameters used in the examples were for powders sprayed using following parameters:

(29) Inlet temperature: about 380 C.

(30) Outlet temperature: about 110 C.

(31) Nozzle Size: about 1.15 mm

(32) Nozzle Pressure: about 15 bar

(33) Chamber Pressure: about 6 millibar

(34) The tenth step comprises pressing the sprayed powder into a green body.

(35) The eleventh step comprises vacuum sintering the green body into a sintered article at a peak temperature between about 2500 F. (1371 C.) and about 2900 F. (1593 C.) for a duration at peak temperature between about 30 minutes and about 120 minutes. One specific sintering parameter used in the examples is a vacuum sinter at a temperature equal to about 2825 F. (1551.6 C.) for a duration equal to about 45 minutes. The following specific properties can be measured: magnetic saturation, coercive force, hardness, density, porosity, and microstructure.

(36) Specific powder batches were produced according to the above process wherein certain properties of these powder batches were measured and reported hereinafter. The powder was pressed and sintered to produce a consolidated, sintered article. Certain properties of the sintered article were measured and reported hereinafter. Table D below sets forth the details of the processes that produced the specific powder batches (i.e., powder of hard material) and articles discussed hereinafter. The objective of the process was to produce a powder of hard material comprising a cemented (cobalt) tungsten carbide powder that is of a composition of between about 93 weight percent and about 94 weight percent tungsten carbide and between about 6 weight percent and about 7 weight percent cobalt.

(37) TABLE-US-00005 TABLE D Specific Process Parameters Process Step Specific Parameters First Step The initial step comprises adding: deionized water (DI Water) in the amount of 1250 grams (25 wt. % of the total powder components which equals 5000 grams) media (5 mm cycloids comprising WC(94 wt %)-Co(6 wt %) wherein the cycloids have a weight of either 21,000 grams (for a media:powder ratio equal to 4.2) or 30,000 grams (for a media:powder ratio equal to 6.0) alkylpolyalkyleneglycolether (i.e., Contraspum K1012 which is a defoamer) in the amount of 10 grams Second Step The second step comprises: adding a mixture of amines and vinyl polymers in an aqueous solution (i.e., Product KM1508 which is an oxidation inhibitor) in the amount of 50 grams (0.28 wt % based on active matter content of the total powder components) with the option of adding Metamax I-15, which is an oxidation inhibitor, in the amount of 115 grams (which is 0.28 wt % based on active matter content of the total powder components) Third Step The third step comprises: adding a wax dispersant (binder) available under the name METAMAX B-4 in the amount of 133 grams (1.46 wt % based on active matter content of the total powder components) Fourth Step The fourth step comprises: adding the powder components of tungsten carbide powder (average particle size of 30-40 microns) and cobalt powder (average particle size 1-2 microns). The total weight of the powder components is 5000 grams with the tungsten carbide powder comprising 4700 grams and the cobalt powder comprising 300 grams. 8-10 hours ball milling Fifth Step The fifth step comprises adding: polyoxyethylene (5) soyaalkylamines which is available under the name Ethomeen, which is a surfactant there were four different amount relating to the Ethomeen content, and they were: no Ethomeen (0 weight percent of the total powder components) 3.75 grams of Ethomeen (0.075 weight percent of the total powder components) 7.50 grams of Ethomeen (0.15 weight percent of the total powder components) 12.5 grams of Ethomeen (0.25 weight percent of the total powder components) Tenth Step spray drying the slurry under the following parameters: Inlet temperature: 380 C. Outlet temperature: 110 C. Nozzle Size: 1.15 mm Nozzle Pressure: 15 bar Chamber Pressure: 6 millibar Eleventh Step The eleventh step comprises vacuum sintering the green body at 2825 F. (1551.6 C.) for 45 minutes

(38) FIG. 1 comprises a graph that reports the average granule size in microns for each of three groupings of powder. Each powder grade comprises about 94 weight percent tungsten carbide and about 6 weight percent cobalt. The compositions shown by the clear bars (i.e., without lining) did not use Ethomeen. The compositions show by the bars with the lining used Ethomeen as a surfactant. Granule size distributions of the powder batches are represented as D.sub.10, D.sub.50 and D.sub.90, where D.sub.50 is the median granule size that splits the granule size distribution with half above and half below this size; 90% of granules fall below D.sub.90 size and 10% of granules are smaller than D.sub.10 size. More specifically, the powder batch that did not use Ethomeen, average D.sub.10 is 7.0 micron, D.sub.50 is 106.0 microns and D.sub.90 is 159.0 microns. For the powder batches that used Ethomeen, the average D.sub.10 is 67.8 microns, D.sub.50 is 115.8 microns and D.sub.90 is 169.9 microns. FIG. 1 shows results that reflect about a 20% increase in the average granule size with the use of Ethomeen in the processing of the powders. Further, the powder batches that used Ethomeen had a narrow size distribution.

(39) Referring to FIG. 2, FIG. 2 is a bar chart that reports the counts of the pores (that have a size greater than 25 microns per unit area) in the sintered article. The technique used to determine the counts for the porosity was ASTM B276-05 (2010) Standard Test Method for Apparent Porosity in Cemented Carbides. The microstructural defects of porosity can play an important role in the fracture initiation, and therefore, there is a need to control the content of porosity to avoid premature failure of the sintered article. Although pressure-sinter operations may reduce the number of pores in the microstructure, such operations add cost to the overall process. As the results below demonstrate, the present invention reduces the porosity in vacuum sintered material without the need to pressure-sinter the article. In the discussion below, as well as throughout the entire application, the use of Ethomeen is synonymous with the scientific term polyoxyethylene (5) soyaalkylamine. There is no intention to limit the scope by the use of Ethomeen instead of polyoxyethylene (5) soyaalkylamine.

(40) In reference to the process parameters, for Bars Nos. 1 and 2, the media:powder ratio was equal to 4.2, the inhibitor was Metamax I-15, and the process did not use Ethomeen. For Bar No. 3, the media:powder ratio was equal to 4.2, the inhibitor was KM1508, and the process did not use Ethomeen. For Bars Nos. 4 and 5, the media:powder ratio was equal to 6.0, the inhibitor was Metamax I-15, and the process did not use Ethomeen. For Bar No. 6, the media:powder ratio was equal to 6.0, the inhibitor was KM1508, and the process did not use Ethomeen. The results reported in FIG. 2 show that the higher media:powder ratio reduced the number of pores (with a size greater than 25 microns per unit area) in the sintered article. The increase in the cycloid weight, as represented by the increase in the media:powder ratio, increases the milling efficiency and improves the dispersion of binders and other organic additives. This improvement in dispersion allows for easier removal of binder during sintering.

(41) Referring to Table 1, Table 1 reports the data that is shown in FIG. 2. The M&P # in Table 1 corresponds to the Powder Batch number in FIG. 2 per the Table E below.

(42) TABLE-US-00006 TABLE E Correspondence between Table 1 and FIG. 2 Table 1 FIG. 2 CT2331274 1 CT2331901 2 CT2034326 3 CT2531119 4 CT2454375 5 CT2454373 6

(43) Referring to FIG. 3, this is a graph that reports the number of pores (that have a size greater than 25 microns per unit area) in the sintered article. The technique used to determine the counts for the porosity was ASTM B276-05 (2010). All of the data reported in FIG. 3 were from a sintered article made via a process in which the media:powder ratio was equal to 6.0. The composition of the article is about 94 weight percent tungsten carbide (coarse grain) and about 6 weight percent cobalt. The data points that are in the form of squares, comprise the results from a sintered article made via a process that did not use Ethomeen and did not use KM1508 as an inhibitor. The data point that is in the form of a circle comprises the results from a sintered article made via a process that did not use Ethomeen, but did use KM 1508 as an inhibitor. The data points that are in the form of a triangle comprises the results from a sintered article that used Ethomeen and also used the inhibitor KM 1508. It becomes apparent from the data reported in FIG. 3 that the use of Ethomeen and the inhibitor KM 1508 reduced the number of pores (that have a size greater than 25 microns per unit area) in the sintered articles.

(44) It appears that the best results (i.e., least number of pores with a size greater than 25 microns per unit area) occur when the Ethomeen (polyoxyethylene (5) soyaalkylamine) is present in an amount equal to or greater than about 0.15 weight percent of the weight of the starting powder components. The KM1508 inhibitor may contain a green-strength additive that can contribute to the drop in the number of pores (that have a size greater than 25 microns per unit area). It also appears that the use of Ethomeen helps with the dispersion of wax, typically used in this process, and subsequently makes the de-binding process during sintering more effective.

(45) Referring to Table 2, Table 2 reports the data that is shown in FIG. 3. The M&P # in Table 2 corresponds to the Powder Batch number in FIG. 3 per the Table F below.

(46) TABLE-US-00007 TABLE F Correspondence between Table 2 and FIG. 3 Table 2 FIG. 3 CT2631119 1 CT2454375 2 CT2454373 3 CT2474995 1 CT2531271 2 CT2536520 3

(47) Referring to FIG. 4, this bar chart reports the pressing pressure for six powder batches that have a composition that comprised about 94 weight percent tungsten carbide and about 6 weight percent cobalt, (or processing parameters). The powder batch represented by the bar with lining was produced without using Ethomeen. The powder batches represented by the clear bars (without lining) were produced by a process using Ethomeen. The 1.2 Die Factor pressing pressure was reduced by about 8 percent in the WCCo coarse grain powder when 0.15 weight percent Ethomeen (polyoxyethylene (5) soyaalkylamine) was used in the aqueous slurry. The 1.2 Die Factor pressing pressure was reduced by about 25 percent in the WCCo coarse grain powder when 0.25 weight percent Ethomeen (polyoxyethylene (5) soyaalkylamine) was used in the aqueous slurry. On average, there is a 13% reduction in the 1.2 Die Factor (DF) pressing pressure resulting from the use of Ethomeen in the process to make the powder batch. There is a contemplation that the drop in the 1.2 Die Factor pressing pressure could be due to an increase in the Scott density, which provides better powder packing characteristics. This provides a benefit in that higher pressing pressures can lead to cracks in the sintered articles and also cause excessive wear on the dies.

(48) Referring to Table 3, Table 3 reports the data that is shown in FIG. 4. The M&P # in Table 3 corresponds to the Powder Batch number in FIG. 4 per the Table G below.

(49) TABLE-US-00008 TABLE G Correspondence between Table 3 and FIG. 4 Table 3 FIG. 4 CT2454373 1 CT2474995 2 CT2531271 3 CT2536520 4 CT2613645 5 CT2613868 6

(50) Referring to FIG. 5, this bar chart reports the milling time for six powder batches that have a composition that comprised about 94 weight percent tungsten carbide and about 6 weight percent cobalt. The bars with lining represent the results from a process wherein the media:powder ratio was equal to 4.2 and the clear bars represent the results from a process wherein the media:powder ratio was equal to 6.0. For Bars Nos. 1 and 2, KM 1508 was used as an inhibitor. For Bars Nos. 3-6, Metamax I-15 was used as inhibitor. The results reported in FIG. 5 show that milling time in hours, which is the time it took to achieve the powder grade specification for the powder, dramatically decreased when using a media:powder ratio equal to 6.0 as compared to a media:powder ratio that was equal to 4.2 when using KM 1508. The results reported in FIG. 5 show that milling time in hours, which is the time it took to achieve the powder grade specification for the powder, dramatically decreased when using a media:powder ratio equal to 6.0 as compared to a media:powder ratio that was equal to 4.2 when using Metamax I-15.

(51) Referring to Table 4, Table 4 reports the data that is shown in FIG. 5 and in FIG. 6. The M&P # in Table 4 corresponds to the Powder Batch number in FIGS. 5 and 6 per the Table H below.

(52) TABLE-US-00009 TABLE H Correspondence between Table 4 and FIGS. 5 and 6 Table 4 FIGS. 5 & 6 CT2034326 1 CT2454373 2 CT2331274 3 CT2331901 4 CT2531119 5 CT2454375 6

(53) Referring to FIG. 6, this is a bar chart that shows the Fe % for three powder batches that have a composition that comprised about 94 weight percent tungsten carbide and about 6 weight percent cobalt. In the processing, the lined bar represents a powder batch processed with the media:powder ratio equal to 4.2 and the clear bars represent a powder batches processed using a process with the media:powder ratio equal to 6.0. FIG. 6 show that the iron (Fe %) contamination dropped from 1.58% after 34 hours of milling to 0.39% after 10 hours when using the Metamax I-15 and 0.28% after 10 hours of milling when using the KM 1508 inhibitor. The results reported in FIG. 6 show that the higher media:powder ratio results in a reduction of the iron contamination.

(54) Referring to Table 4, Table 4 reports the data that is shown in FIG. 7. The M&P # in Table 4 corresponds to the Powder Batch number in FIG. 7 per the Table 1 below.

(55) TABLE-US-00010 TABLE I Correspondence between Table 4 and FIG. 7 Table 4 FIG. 7 CT2331901 4 CT2531119 5 CT2454375 6

(56) Referring to FIG. 7, this chart provides a summary of benefits by using a higher media:powder ratio, Ethomeen and KM 1508 on pores (size greater than 25 microns per unit area). KM1508 contains green strength additive. It shows that best results are obtained (i.e. zero porosity) using a higher media:powder ratio, KM1508 and Ethomeen.

(57) Set forth below are Table 1 through 4, which report data shown in graph form in the earlier figures.

(58) TABLE-US-00011 TABLE 1 Effect of media:powder ratio on porosity count (that have size greater than 25 microns per unit area) Milling Inhibitor Surfactant Binder Defoamer Time Media: Porosity M & P # Type wt. % Type wt. % Type wt. % Type wt. % (hrs) Powder count CT2331274 Aqueous Amines 0.28 None 0 Wax 1.46 Alkylpolyalkyleneglycolether 0.2 34 4.2 60 Dispersion CT2331901 Aqueous Amines 0.28 None 0 Wax 1.46 Alkylpolyalkyleneglycolether 0.2 34 4.2 107 Dispersion CT2034326 Aqueous Amines & 0.28 None 0 Wax 1.46 Alkylpolyalkyleneglycolether 0.2 20 4.2 200 Vinyl Polymers Dispersion CT2531119 Aqueous Amines 0.28 None 0 Wax 1.46 Alkylpolyalkyleneglycolether 0.2 10 6 33 Dispersion CT2454375 Aqueous Amines 0.28 None 0 Wax 1.46 Alkylpolyalkyleneglycolether 0.2 10 6 20 Dispersion CT2454373 Aqueous Amines & 0.28 None 0 Wax 1.46 Alkylpolyalkyleneglycolether 0.2 10 6 7 Vinyl Polymers Dispersion

(59) TABLE-US-00012 TABLE 2 Effect of KM508 and Ethomeen on porosity count (that have size greater than 25 microns per unit area) Milling Inhibitor Surfactant Binder Defoamer Time Media: Porosity M & P # Type wt. % Type wt. % Type wt. % Type wt. % (hrs) Powder Count CT2531119 Aqueous 0.28 None 0 Wax 1.46 Alkylpolyalkylene- 0.2 10 6 33 Amines Dispersion glycolether CT2454375 Aqueous 0.28 None 0 Wax 1.46 Alkylpolyalkylene- 0.2 10 6 20 Amines Dispersion glycolether CT2454373 Aqueous 0.28 None 0 Wax 1.46 Alkylpolyalkylene- 0.2 10 6 7 Amines & Vinyl Dispersion glycolether Polymers CT2474995 Aqueous 0.28 Polyoxyethylene (5) 0.15 Wax 1.46 Alkylpolyalkylene- 0.2 10 6 0 Amines & Vinyl soyaalkylamines Dispersion glycolether Polymers CT2531271 Aqueous 0.28 Polyoxyethylene (5) 0.15 Wax 1.46 Alkylpolyalkylene- 0.2 9 6 0 Amines & Vinyl soyaalkylamines Dispersion glycolether Polymers CT2536520 Aqueous 0.28 Polyoxyethylene (5) 0.15 Wax 1.46 Alkylpolyalkylene- 0.2 9 6 0 Amines & Vinyl soyaalkylamines Dispersion glycolether Polymers

(60) TABLE-US-00013 TABLE 3 Effect of Ethomeen on pressing pressure 1.2 DF Milling Pressing Inhibitor Surfactant Binder Defoamer Time Media: Pressure M & P # Type wt. % Type wt. % Type wt. % Type wt. % (hrs) Powder (TSI) CT2454373 Aqueous Amines & 0.28 None 0 Wax 1.46 Alkylpolyalkylene- 0.2 10 6 12.0 Vinyl Polymers Dispersion glycolether CT2474995 Aqueous Amines & 0.28 Polyoxyethylene (5) 0.15 Wax 1.46 Alkylpolyalkylene- 0.2 10 6 11.0 Vinyl Polymers soyaalkylamines Dispersion glycolether CT2531271 Aqueous Amines & 0.28 Polyoxyethylene (5) 0.15 Wax 1.46 Alkylpolyalkylene- 0.2 9 6 9.1 Vinyl Polymers soyaalkylamines Dispersion glycolether CT2536520 Aqueous Amines & 0.28 Polyoxyethylene (5) 0.15 Wax 1.46 Alkylpolyalklene- 0.2 9 6 10.8 Vinyl Polymers soyaalkylamines Dispersion glycolether CT2613645 Aqueous Amines & 0.28 Polyoxyethylene (5) 0.15 Wax 1.46 Alkylpolyalkylene- 0.2 8.4 6 10.49 Vinyl Polymers soyaalkylamines Dispersion glycolether CT2613868 Aqueous Amines & 0.28 Polyoxyethylene (5) 0.15 Wax 1.46 Alkylpolyalkylene- 0.2 8.4 6 10.68 Vinyl Polymers soyaalkylamines Dispersion glycolether

(61) TABLE-US-00014 TABLE 4 Effect of media:powder ratio on milling time and Fe contamination Milling Inhibitor Surfactant Binder Defoamer Time Media: M & P # Type wt. % Type wt. % Type wt. % Type wt. % (hrs) Powder Fe % CT2034326 Aqueous Amines & 0.28 None 0 Wax 1.46 Alkylpolyalkyleneglycolether 0.2 20 4.2 Vinyl Polymers Dispersion CT2454373 Aqueous Amines & 0.28 None 0 Wax 1.46 Alkylpolyalkyleneglycolether 0.2 10 6 0.28 Vinyl Polymers Dispersion CT2331274 Aqueous Amines & 0.28 None 0 Wax 1.46 Alkylpolyalkyleneglycolether 0.2 34 4.2 Dispersion CT2331901 Aqueous Amines 0.28 None 0 Wax 1.46 Alkylpolyalkyleneglycolether 0.2 34 4.2 1.58 Dispersion CT2531119 Aqueous Amines 0.28 None 0 Wax 1.46 Alkylpolyalkyleneglycolether 0.2 10 6 0.39 Dispersion CT2454375 Aqueous Amines 0.28 None 0 Wax 1.46 Alkylpolyalkyleneglycolether 0.2 10 6 0.33 Dispersion

(62) It becomes apparent that there are many benefits that result from the present invention. These benefits are set forth below.

(63) The use of the higher media:powder ratio along with the addition of KM1508 and Ethomeen reduce the number of pores (that have a size greater than 25 microns per unit area) in the microstructure of the sintered article. This is an important benefit because microstructural defects like porosity typically reduce the useful life of the sintered article.

(64) The use of Ethomeen drops the pressing pressure for the powder batch material. A reduction in the pressing pressure necessary for satisfactory compaction of the powder into the green body is thought to minimize die wear as well as cracking in the sintered article.

(65) The use of a higher media:powder ratio reduces the milling time necessary to achieve the specified powder properties. A reduction in the milling time reduces production costs and can increase production capacity without adding additional equipment. The high media:powder ratio also results in a reduction of the iron contamination (Fe %) during the milling. Lower iron contamination during the milling minimizes metallurgical defects in the sintered article.

(66) The use of Ethomeen increases the granule size of the powder batch and results in the production of powder batches with narrow granule size distributions. These are advantageous properties for the powder batch material since the granule size of the cemented carbide controls powder flow, pressing pressure and sintering response. The use of Ethomeen also facilitates with the powder slurry discharge from the ball mill. This is an advantageous property for the efficient production of the powder batch material since it saves processing time and improves powder yield.

(67) The patents and other documents identified herein are hereby incorporated by reference herein. Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification or a practice of the invention disclosed herein. It is intended that the specification and examples are illustrative only and are not intended to be limiting on the scope of the invention. The true scope and spirit of the invention is indicated by the following claims.