1、Designation: A923 14Standard Test Methods forDetecting Detrimental Intermetallic Phase in DuplexAustenitic/Ferritic Stainless Steels1This standard is issued under the fixed designation A923; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re
2、vision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 The purpose of these test methods is to allow detectionof the presence of intermetallic phases in
3、 duplex stainless steelsto the extent that toughness or corrosion resistance is affectedsignificantly. These test methods will not necessarily detectlosses of toughness or corrosion resistance attributable to othercauses.1.2 Duplex (austenitic-ferritic) stainless steels are suscep-tible to the forma
4、tion of intermetallic compounds duringexposures in the temperature range from approximately 600 to1750F (320 to 955C). The speed of these precipitationreactions is a function of composition and thermal or thermo-mechanical history of each individual piece. The presence ofthese phases is detrimental
5、to toughness and corrosion resis-tance.1.3 Correct heat treatment of duplex stainless steels caneliminate these detrimental phases. Rapid cooling of theproduct provides the maximum resistance to formation ofdetrimental phases by subsequent thermal exposures.1.4 Compliance with the chemical and mecha
6、nical require-ments for the applicable product specification does not neces-sarily indicate the absence of detrimental phases in the product.1.5 These test methods include the following:1.5.1 Test Method ASodium Hydroxide Etch Test forClassification of Etch Structures of Duplex Stainless Steels(Sect
7、ions 37).1.5.2 Test Method BCharpy Impact Test for Classificationof Structures of Duplex Stainless Steels (Sections 813).1.5.3 Test Method CFerric Chloride Corrosion Test forClassification of Structures of Duplex Stainless Steels (Sec-tions 1420).1.6 The presence of detrimental intermetallic phases
8、isreadily detected in all three tests, provided that a sample ofappropriate location and orientation is selected. Because theoccurrence of intermetallic phases is a function of temperatureand cooling rate, it is essential that the tests be applied to theregion of the material experiencing the condit
9、ions most likelyto promote the formation of an intermetallic phase. In the caseof common heat treatment, this region will be that whichcooled most slowly. Except for rapidly cooled material, it maybe necessary to sample from a location determined to be themost slowly cooled for the material piece to
10、 be characterized.1.7 The tests do not determine the precise nature of thedetrimental phase but rather the presence or absence of anintermetallic phase to the extent that it is detrimental to thetoughness and corrosion resistance of the material.1.8 Examples of the correlation of thermal exposures,
11、theoccurrence of intermetallic phases, and the degradation oftoughness and corrosion resistance are given in Appendix X1and Appendix X2.1.9 The values stated in either inch-pound or SI units are tobe regarded as the standard. The values given in parenthesesare for information only.1.10 This standard
12、 does not purport to 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
13、Standards:2A370 Test Methods and Definitions for Mechanical Testingof Steel Products1These test methods are under the jurisdiction of ASTM Committee A01 onSteel, Stainless Steel and Related Alloysand are the direct responsibility ofSubcommittee A01.14 on Methods of Corrosion Testing.Current edition
14、approved March 1, 2014. Published March 2014. Originallyapproved in 1994. Last previous edition approved in 2008 as A923 08. DOI:10.1520/A0923-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards
15、 volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1G48 Test Methods for Pitting and Cre
16、vice Corrosion Resis-tance of Stainless Steels and Related Alloys by Use ofFerric Chloride SolutionTEST METHOD ASODIUM HYDROXIDE ETCHTEST FOR CLASSIFICATION OF ETCHSTRUCTURES OF DUPLEX STAINLESS STEELS3. Scope3.1 The sodium hydroxide etch test may be used for theacceptance of material but not for re
17、jection. This test methodmay be used with other evaluation tests to provide a rapidmethod for identifying those specimens that are free ofdetrimental intermetallic phases as measured in these othertests.3.2 The sodium hydroxide etch test may be used to screenspecimens intended for testing in Test Me
18、thod B, CharpyImpact Test for Classification of Structures of Duplex StainlessSteels, and in Test Method C, Ferric Chloride Corrosion Testfor Classification of Structures of Duplex Stainless Steels.3.3 Reference photomicrographs are provided to show clas-sifications of etch structures of a particula
19、r stainless steel typethat are equivalent to acceptable or to possibly unacceptableperformance for each practice. When Test Method A is used asa screening test for Test Method B or Test Method C,specimens having acceptable etch structures need not besubjected to Test Method B or Test Method C.3.4 Ta
20、ble 1 indicates the applicability and acceptance crite-ria for Test Method A. When Test Method A is specified as anacceptance test, specimens having other than acceptable etchstructures may, at the option of the producer, be tested by TestMethod B or Test Method C.3.5 The steel shall be tested in th
21、e final solution heat treatedcondition or such other conditions as are agreed upon betweenthe producer and the user.4. Apparatus4.1 Source of Direct CurrentBattery, generator, or rectifiercapable of supplying approximately 15 V and 20 A.4.2 AmmeterRange from 0 to 30 A (see Note 1).4.3 Variable Resis
22、tance (see Note 1).4.4 CathodeA cylindrical piece of conductive metal.4.5 Large Electric Clamp, to hold the specimen to beetched.4.6 Metallurgical Microscope, for examination of etchedmicrostructures to 400 to 500 diameters.4.7 Electrodes of the Etching CellThe specimen to beetched is made the anode
23、, and a cylindrical piece of metal aslarge as the specimen to be etched is made the cathode.4.8 Electrolyte, sodium hydroxide (NaOH), reagent grade.NOTE 1The variable resistance and ammeter are placed in the circuitto measure and control the current on the specimen to be etched.5. Preparation of Tes
24、t Specimens5.1 For mill products, examination shall be made on alongitudinal or transverse section. For cast products, examina-tion shall be made on a separately cast test coupon which washeat treated in the same furnace load as the casting itrepresents. Unless otherwise specified, selection of the
25、testcoupon size shall be at the discretion of the producer. Becausehigh temperature or mechanical deformation associated withparticular cutting processes may alter the structure of the steel,the cutting of the test specimen should be by a technique thatprevents these effects. Alternatively, after th
26、e specimens arecut, any material that may have been affected by high tempera-ture or deformation associated with the cutting should beremoved by machining or wet grinding prior to testing.5.2 For mill products, the specimen should allow for asurvey across the full thickness of the section or, in the
27、 case ofa heavy section, a survey from one surface through themid-thickness of the section. The specimen shall include themid-thickness.5.3 For cast materials, the specimen shall be taken atapproximately 1/4T.5.4 PolishingOn all materials, cross-sectional surfacesshould be polished to a metallograph
28、ic finish suitable forexamination at 400 after etching. Specimens containing weldsshould include base metal, weld heataffected zone, and weldmetal. The area to be etched may be prepared by grinding to an80- or 120-grit finish on a grinding belt or wheel withoutexcessive heating and then by polishing
29、 on successively fineremery papers, No. 1,12,10,20,30, and finer. Other methods ofpolishing may be acceptable.5.5 Etching SolutionThe solution for etching is preparedby adding 40 g of reagent grade sodium hydroxide (NaOH) to100 g of distilled water.5.6 Etching ConditionsThe polished specimen should
30、beetched at approximately 1 to 3 V dc, for 5 to 60 s (see Note 2).NOTE 2When etching is performed at 1 to 3 V dc with a platinumcathode for 5 to 60 s, any intermetallic phase is revealed by yellow, thenbrown, staining, followed by staining of the ferrite.5.7 RinsingFollowing etching, the specimen sh
31、ould berinsed thoroughly in hot water and in acetone or alcohol,followed by air drying.6. Classification of Etch Structures6.1 The etched surface shall be examined on a metallurgicalmicroscope at 400 to 500.TABLE 1 Applicability and Acceptance Criteria forTest Method AGradeAcceptableEtch StructureNo
32、nacceptableEtch StructureS31803, S32205,S32750, S32760,S32550,S32520,J92205, J93404unaffectedstructure (Fig. 1,Fig. 2)possibly affectedstructure (Fig. 3, Fig. 4)affected structure (Fig. 5,Fig. 6)centerline structure (Fig.7)A923 1426.2 The etched cross-sectional areas should be examinedthoroughly by
33、complete traverse of the full sample and acrossall zones such as weld metal, weld-affected zones, and basemetal on specimens containing welds.6.3 The etch structures are classified into the followingtypes:6.3.1 Unaffected Structure (Fig. 1, Fig. 2)The ferrite hasbeen etched without revelation of int
34、ermetallic phase. Theinterphase boundaries are smooth.6.3.2 Possibly Affected Structure (Fig. 3, Fig. 4)Theferrite has been etched with isolated indications of possibleintermetallic phase. The interphase boundaries may show a finewaviness.6.3.3 Affected Structure (Fig. 5, Fig. 6)The indications ofan
35、 intermetallic phase are readily revealed before or simulta-neously with the staining of the ferrite during etching.6.3.4 Centerline Structure (Fig. 7)An intermetallic phaseis observed as a continuous or semi-continuous phase in themid-thickness region of the product, with or without theaffected str
36、ucture outside of the mid-thickness region, indica-tive of segregation.7. Interpretation and Use of the Etch StructureClassifications7.1 When Test Method A is used as a screening test, the useof these etch structures depends on the test method for whichthe specimens are being screened. Important cha
37、racteristics ofeach of the test methods are described as follows.7.2 Test Method BThe Charpy impact test detects reduc-tions in toughness from that of the optimal composition andprocessing. Such reductions may be attributable to intermetal-lic phases or to other causes not necessarily detectable by
38、TestMethod A. A Possibly Affected Structure is likely to beassociated with a loss of Charpy impact toughness rangingfrom slight to severe. An Affected Structure is associated withFIG. 1 Unaffected Structure in S31803: (a) Longitudinal Sectionand (b) Transverse Section (500 Magnification Before Repro
39、duc-tion)FIG. 2 (a) J92205: Unaffected Structure-Statically Cast (400 Mag-nification)FIG. 2 (b) J92205: Unaffected Structure-Centrifugally Cast (400Magnification) (continued)A923 143a severe loss of Charpy impact toughness. A CenterlineStructure may or may not be detected by a Charpy test,depending
40、on the orientation of the Charpy specimen.7.3 Test Method CThe ferric chloride corrosion test is a24-h test in 10 % ferric chloride. It will detect a loss ofcorrosion resistance associated with local depletion of chro-mium and molybdenum as a result of the precipitation ofchromium-rich and possibly
41、molybdenum-rich phases, notlimited to intermetallic phases. An Affected Structure is asso-ciated with significant weight loss in the corrosion test. APossibly Affected Structure is likely to be associated withsignificant weight loss in the corrosion test.TEST METHOD BCHARPY IMPACT TEST FORCLASSIFICA
42、TION OF STRUCTURES OFDUPLEX STAINLESS STEELS8. Scope8.1 This test method describes the procedure for conductingthe Charpy impact test as a method of detecting the precipita-tion of detrimental intermetallic phases in duplex stainlesssteels. The presence or absence of an indication of intermetallicph
43、ase in this test is not necessarily a measure of performanceof the material in service with regard to any property other thanthat measured directly. The Charpy procedure as here appliedis different from that as commonly applied for the determina-tion of toughness and should not be used when characte
44、rizationof material toughness is the purpose of the testing.8.2 The Charpy impact test may be used to evaluate mill andcast products, provided that it is possible to obtain a specimenof relevant location and geometry.8.3 Table 2 indicates the applicability and acceptance crite-ria for Test Method B.
45、9. Rapid Screening Test9.1 Before testing by the Charpy impact test, specimens ofthe steel may be given a rapid screening test in accordance withFIG. 3 Possibly Affected Structure in S31803: (a) LongitudinalSection and (b) Transverse Section (500 Magnification BeforeReproduction)FIG. 4 (a) J92205: P
46、ossibly Affected Structure-Statically Cast(400 Magnification)FIG. 4 (b) J92205: Possibly Affected Structure-Centrifugally Cast(400 Magnification) (continued)A923 144the procedures of Test MethodA, Sodium Hydroxide Etch Testfor Classification of Etch Structures of Duplex Stainless Steels.Preparation,
47、 etching, and the classification of etch structuresare described therein. Specimens having an etch structuredescribed as Unaffected Structure in Test Method A will beessentially free of detrimental effect on impact toughnessrelated to the formation of intermetallic phase. Other mecha-nisms for loss
48、of toughness may occur independently but arebeyond the scope of this test method. Specimens showingUnaffected Structure in Test Method A are acceptable withrespect to the absence of intermetallic phases, without thenecessity of performing the Charpy test as described in TestMethod B. All specimens h
49、aving other than Unaffected Struc-ture shall be tested by the Charpy impact test.10. Apparatus10.1 The test apparatus shall be as described in TestMethods and Definitions A370.FIG. 5 Affected Structure in 8a S31803: (a) Longitudinal Sectionand (b) Transverse Section (500 Magnification Before Reproduc-tion)FIG. 6 J92205: Affected Structure (400 Magnification)FIG. 7 S31803: Longitudinal Section (500 Magnification BeforeReproduction)TABLE 2 Applicability and Acceptance Criteria forTest Method BGrade ConditionTestTemperatureMinimum ImpactEne
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