1、Designation: B 890 07Standard Test Method forDetermination of Metallic Constituents of Tungsten Alloysand Tungsten Hardmetals by X-Ray FluorescenceSpectrometry1This standard is issued under the fixed designation B 890; the number immediately following the designation indicates the year oforiginal ad
2、option or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes a procedure for the determi-nation of the
3、concentration, generally reported as mass percent,of the metallic constituents of tungsten-based alloys andhardmetals utilizing wavelength dispersive X-ray fluorescencespectrometry (XRF). This test method incorporates the prepa-ration of standards using reagent grade metallic oxides,lithium-borate c
4、ompounds, and fusion techniques. This testmethod details techniques for preparing representative speci-mens of both powder and sintered tungsten-based material.This test method is accurate for a wide range of compositions,and can be used for acceptance of material to grade specifica-tions.1.2 This t
5、est method is applicable to mixtures of tungsten ortungsten carbide with additions of refractory metal carbidesand binder metals. Table 1 lists the most common elementalconstituents and their concentration range. Note that many ofthese occur as metallic carbides.1.3 This standard does not purport to
6、 address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 135 Ter
7、minology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE 1361 Guide for Correction of Interelement Effects inX-Ray Spectrometric Analysis2.2 Handbook of Chemistry and Physics,367th ed3. Terminology3.1 For definitions of terms used in this test method, refer toTerminology E 1
8、35.4. Summary of Test Method4.1 A suite of standards which closely match the chemicalcontent of the material to be analyzed are prepared usingreagent grade metallic oxides. Test samples are oxidized in ahigh-temperature furnace open to air. Fused glass specimensare prepared for these standards and f
9、or the test samples to beanalyzed. These specimens of oxidized tungsten or tungstencarbide alloys are irradiated with an energetic primary X-raybeam. The intensity of the resultant secondary X-rays, charac-teristic in energy, for each elemental constituent is measured bymeans of a suitable detector
10、or combination of detectors afterdiffraction by a Bragg spectrometer. The concentration of eachconstituent element is calculated by comparison with standardsamples which closely match the chemical content of theanalyzed material. The calculation may be manual, incorporatea calibration curve, or be p
11、erformed by a computer programwhich incorporates correction routines for X-ray absorptionand enhancement effects (see Guide E 1361).5. Significance and Use5.1 This test method allows the determination of the chemi-cal composition of powdered and sintered tungsten-basedhardmetals. This test method is
12、 not applicable to materialwhich will not oxidize readily at high temperatures in air, suchas tungsten/copper or tungsten/silver alloys.1This test method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mittee B09.06
13、 on Cemented Carbides.Current edition approved March 15, 2007. Published April 2007. Originallyapproved in 1998. Last previous edition approved in 2002 as B 890 02.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Boo
14、k of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3CRC Press, Boca Raton, FL, 1987.TABLE 1 Elemental Constituents and Concentration RangeElement Concentration, Mass %(minimum - maximum)Chromium (Cr) 0.05 - 5.0Cobalt (Co) 0.05 - 40Hafnium (Hf) 0.05
15、 - 2.0Iron (Fe) 0.05 - 2.0Molybdenum (Mo) 0.05 - 5.0Nickel (Ni) 0.05 - 30Niobium (Nb) 0.05 - 15Tantalum (Ta) 0.05 - 30Titanium (Ti) 0.05 - 30Vanadium (V) 0.05 - 2.01Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 This test method
16、specified lithium-borate compoundsfor the glass fusion material. However, numerous other choicesare available. These include other lithium-borate compounds,sodium carbonate and borate mixtures, and others. The meth-odology specified here is still applicable as long as the samefusion mixture is used
17、for both standards and specimens.6. Interferences6.1 Errors in XRF-determined compositional values may beencountered due to X-ray enhancement and absorption effectsdependent on the elements present and the X-ray line beingmeasured for a specific element. This effect can be reduced bydetermination of
18、 correction factors using appropriate standardsand interelement correction routines, manual or computerized.6.2 Accuracy and precision of the analytical results obtainedfrom molybdenum-containing samples may be rendered unre-liable due to the sublimation and evaporation of molybdenumfrom the materia
19、l during the oxidation step in specimenpreparation.6.3 Incorporation of the fusion method of specimen prepa-ration will:6.3.1 Reduce the deleterious influence of particle size ef-fects experienced when analyzing powder materials by varyingparticle size.6.3.2 Reduce inhomogenieties within a sample.6.
20、3.3 Improve penetration of X rays.6.3.4 Reduce interelement interferences by tungsten on allother elements.7. Apparatus7.1 X-Ray Fluorescence Wavelength Dispersive Spectrom-eter7.2 FluxerAn automated high-temperature mixing devicecapable of melting, mixing, and pouring a molten liquidspecimen into a
21、 proper casting dish, is highly preferred7.3 Analytical Balance, readability of 0.00001 g7.4 Toploading Balance, readability of 0.001 g7.5 Ordinary Laboratory Apparatus.7.6 One Pt - 5 % Au Casting Dish (minimum)7.7 One Pt - 5 % Au Crucible (minimum)7.8 Platinum Tipped Tongs7.9 Weighing Paper7.10 Che
22、mical Spoon and Scoopula7.11 Ceramic Combustion Boat7.12 High Temperature Tube or Muffle Furnace, open to theatmosphere7.13 Self-adhering Stickers,34 by 1 in.7.14 High-Temperature marking pen7.15 Ceramic Mortar and Pestle7.16 Tungsten Carbide Mortar and Pestle7.17 Miniature Mixer, optional8. Reagent
23、s and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specification of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.4Other grade
24、s may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.8.2 Di-lithiumtetraborate (Li2B4O7):Lithiummetaborate(LiBO2), 66 + 34.8.3 Lithium Bromide(LiBr).8.4 Metallic Oxide Powder, highest oxidat
25、ion state forelements of interest; that is Co3O4,Cr2O3,Fe3O4, HfO2,MoO3,Nb2O5, NiO, Ta2O5,TiO2,V2O5, and WO3WarningSeveral of the metallic oxides used in this testmethod are highly toxic and possibly carcinogenic, such asCr2O3, NiO, or V2O5. Extreme care should be used at all timeswhen handling this
26、 material (especially V2O5). All mixing ofstandards should be performed in a fume hood. All of thelithium compounds are water-soluble and therefore able to beabsorbed into the body by inhalation and possibly by absorp-tion through the skin. This material should be weighed in afume hood.8.5 Citric Ac
27、id (HOC(COOH)(CH2COOH)2.8.6 Silicic Acid (SiO2xH20).9. Specimen Preparation9.1 Prepare specimens of the material to be analyzed byoxidizing, weighing, and fusing starting powders, chips, orcrushed sintered hard metal samples.9.2 Place 3 to5gofpowdered specimen in a labeledceramic combustion boat. If
28、 a sintered sample is to beanalyzed, then the sample must be crushed or pulverized intosmall pieces or chips must be produced by machining prior toplacement in the combustion boat. To crush or pulverize asample, a tungsten carbide mortar and pestle should be used toreduce the incidence of contaminat
29、ion.9.3 Oxidize the specimen in the heat zone of a high-temperature tube or muffle furnace open to the atmosphere at825 6 25C. All specimens must be oxidized.9.4 When the specimen has been completely oxidized (4 to6 h), remove from the furnace and allow to cool.NOTE 1Complete oxidation of a sintered
30、 magnetic tungsten hardmetal sample can be checked by testing the cool oxidized chips with amagnet. If any of the chips are still magnetic, recrush the sample and placeback in the furnace for further oxidation.9.5 Pour the specimen onto a clean sheet of paper or into aclean mortar and gently crush w
31、ith a pestle.9.6 Transfer the specimen to a labeled specimen vial.9.7 In a fume hood, weigh out 15.000 6 0.001 g of thedilithium tetraborate: lithiummetaborate mixture, 1.5 6 0.001g of the silicic acid, and 0.200 6 0.001 g of LiBr and transferto a clean sample vial. This mixture will be referred to
32、as the“fusion mixture.” Seal and store until needed.NOTE 2Other fusion materials can be used. See 5.2.4Reagent Chemicals, American Chemical Society Specification, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Anal
33、ar Standards for LaboratoryChemicals, BDH Ltd,. Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulatory, U.S. Pharmaceutical Convention, Inc. (USPC), Rock-vale, MD.B8900729.8 In a fume hood, transfer the fusion mixture to a platinumcrucible immediately prior to weighing of th
34、e oxidized samplematerial.9.9 Weigh out 1.0000 6 0.00005 g of oxidized specimenand transfer to the platinum crucible. Mix gently with thefusion mixture.NOTE 3If there is not enough sample to make a standard fusion, or theamount of the total mixture is too large for the casting dish, proportionateamo
35、unts of oxidized test sample and fusion mixture can be utilized toprepare a specimen recognizing that larger fractional errors may beincurred in the analysis. This should only be used when absolutelynecessary.9.10 Using the fluxer, melt the specimen at 1300 6 100Cand cast into a heated platinum cast
36、ing dish.9.10.1 WarningThe process of making glass fusionsexposes personnel to high-temperature liquids. Extreme careshould be exercised while preparing these samples. These hightemperatures also cause some volatilization of the lithiumcompounds. The fluxer should have an exhaust hood to removethese
37、 gases from the facility. The lithium compounds used inthis procedure are hygroscopic. Material open to the atmo-sphere for an extended period of time will absorb moisture.Exposure of this material to subsequent high heat will causerapid formation of steam and may cause spattering of themolten glass
38、 onto the instrument and possibly the operator.9.11 While the fused specimen is cooling, remove thecrucible from the instrument with the platinum-tipped tongsand cool under a stream of water.9.12 Place the crucible in a 1000-mL beaker which has a2-volume percent solution of citric acid. Put the beak
39、er on a hotplate and warm the solution. The crucible should be clean inapproximately 30 min. Remove the crucible from the acid bathwith tongs and rinse with water. Dry the crucible and store.9.13 When the fused specimen is cool, remove from thecasting dish by gripping the dish firmly with tongs, tur
40、ning thedish over, and gently tapping against a clean paper. The dishand fused specimen should cleanly separate. Label the fusedspecimen with a self-adhering tag.NOTE 4Any evidence of wetting between the specimen and theplatinum crucible or casting dish is an indication that the specimen hasreacted
41、with these vessels and is not a valid representative sample.9.14 If the fusion crystallizes or fractures on cooling, crushthe fusion and recast. If the fused specimen cannot be removedfrom the platinum casting dish with very light tapping, dissolvethe specimen from the dish using a warm 2-volume per
42、centcitric acid solution. Prepare a new specimen in accordance with9.7-9.10.CautionExcessive prying or tapping of the crystallizedspecimen while it is in the dish will damage the platinum ware.10. Standardization of Spectrometer and Analysis10.1 Based on the X-ray spectrometer configuration andinstr
43、ument manufacturers operating instructions, determinethe instrument operating parameters to provide optimum spec-tral analysis for each element being analyzed in a given matrix.Table 2 provides the approximate X-ray peak positions (Braggangle - 2Q) and crystals recommended for each of the elementsof
44、 interest.10.2 If required, normalize the X-ray spectrometer operat-ing parameters to obtain the appropriate secondary x-rayintensities from the reference standards utilized.10.3 Measure X-ray intensities on a sufficient number offused standards to establish a calibration curve (intensityversus conc
45、entration of analyte) for each element of interest.NOTE 5The number of standards sufficient to establish a calibrationcurve is dependent on the range of concentrations to be analyzed for eachelement. In all cases, a minimum of six standards is required.10.4 Calibration curves may be established manu
46、ally, orcorrections for interelement effects may be calculated usingXRF vendor-supplied computer software.NOTE 6Accuracy of a given interelement correction routine can beverified by including one or more reference standards as “blind” un-knowns as part of an analysis.11. Procedure11.1 Obtain X-ray i
47、ntensity data from the fused test speci-mens.11.2 Calculate relative concentrations utilizing appropriatecalibration curves and absorption and enhancement correctionroutines, if available.12. Report12.1 Report the results of the analysis as mass percent of themetallic or carbide constituent. Report
48、average values ofreplicate determinations, either measurements or samples, ifperformed, along with the concentration range. The correctionroutine employed to determine final concentration valuesshould also be specified by the party completing the analysis,if required.12.2 The parties involved may re
49、quire reporting of theactual X-ray spectrometer operating parameters employed foreach element of interest. These typically include:12.2.1 Specimen form,12.2.2 X-ray source type,12.2.3 X-ray tube operating conditions, kV and mA,12.2.4 X-ray line analyzed,12.2.5 Diffracting crystal,12.2.6 Type of detector, and12.2.7 X-ray path whether vacuum, air, or inert gas.13. Precision and Bias13.1 PrecisionThe repeatability standard deviation of ma-jor constituents has been determined to be 0.25 % of theTABLE 2 Analytical X-ray LinesElementSymbolShellSeriesReflectionOrderBraggAn
