1、Designation: G209 12aG209 13Standard Practice forDetecting mu-phase in Wrought Nickel-Rich, Chromium,Molybdenum-Bearing Alloys1This standard is issued under the fixed designation G209; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, 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 This practice incorporates etching and metallographic examination of Wrought Nickel-Rich, Chromium, Mol
3、ybdenum-Bearing Alloys such as, but not limited to, UNS N06686 and UNS N10276.1.2 Microstructures have a strong influence on properties and successful application of metals and alloys. The presence ofmu-phase in the microstructure may significantly reduce the corrosion resistance of Wrought Nickel-R
4、ich, Chromium, andMolybdenum-Bearing Alloys.1.3 This practice may be used to determine the presence of mu-phase in Wrought Nickel-Rich, Chromium, and Molybdenum-Bearing Alloys through comparison of microstructure observed for etched metallographic specimens to a glossary ofphotomicrographs displayin
5、g the presence and absence of mu-phase in the microstructure.1.4 The values stated in SI units are to be regarded as the standard. Other units are given in parentheses for information only.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It i
6、s the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterE3 Guide for Preparation of Metallographic Speci
7、mensE7 Terminology Relating to MetallographyE1245 Practice for Determining the Inclusion or Second-Phase Constituent Content of Metals by Automatic Image AnalysisE1268 Practice for Assessing the Degree of Banding or Orientation of MicrostructuresG193 Terminology and Acronyms Relating to Corrosion3.
8、Terminology3.1 Definitions:3.1.1 The terminology used herein, if not specifically defined otherwise, shall be in accordance with Terminology G193.Definitions provided herein and not given in Terminology G193 are limited only to this practice.3.1.2 For metallographic definitions used in this practice
9、, refer to Terminology E7.3.1.3 For evaluation of inclusions, secondary phases and banding, if desired, refer to Practices E1245 and E1268.3.2 Definitions of Terms Specific to This Standard:3.2.1 mu-phase (), nrhombohedral phase which may occur in Nickel-Rich, Chromium, Molybdenum-Bearing Alloys and
10、may occur as coarse, irregular platelets, which form at high temperature.4. Significance and Use4.1 These test methods describe laboratory tests to determine the presence of mu-phase in Wrought Nickel-Rich, Chromium,and Molybdenum-Bearing Alloys through comparison of microstructure observed for etch
11、ed metallographic specimens to a1 This test method is under the jurisdiction of ASTM Committee G01 on Corrosion of Metals and is the direct responsibility of Subcommittee G01.05 on LaboratoryCorrosion Tests.Current edition approved Nov. 15, 2012May 1, 2013. Published December 2012May 2013. Originall
12、y approved in 2012. Last previous edition approved in 2012 asG20912.12a. DOI: 10.1520/G020912A.10.1520/G0209-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the s
13、tandards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accur
14、ately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor
15、Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1glossary of photomicrographs displaying the presence and absence of mu-phase in the microstructure. The presence of mu-phasein the microstructure may significantly reduce the corrosion resistance, strength, toughness and ductility o
16、f Wrought Nickel-Rich,Chromium, and Molybdenum-Bearing Alloys.5. Sample Preparation and Etching35.1 Sectioning:5.1.1 The selection of test specimens for metallographic examination is extremely important because, if their interpretation isto be of value, the specimens must be representative of the ma
17、terial that is being studied and shall be per location E (longitudinalsection perpendicular to rolled surface) for plate and sheet and per location G (radial longitudinal section) for rod and bar per Fig.1 (Guide E3). The intent or purpose of the metallographic examination will usually dictate the l
18、ocation of the specimens to bestudied. For rod and bar test specimens specifically, samples are taken from -diameter per location G as seen in Fig. 1. Triplicatetest specimens shall be evaluated for determination of the presence of mu-phase.5.1.2 Cut the specimen to a convenient size using any of va
19、rious types of silicon carbide, diamond, boron carbide or othercarbide cutoff blades. Deformation damage can be minimized by using thin cutoff wheels 0.78 mm (132 in.) thick as opposed to1.58 mm (116 in.). Never cut dry. Use of adequate water coolant is desired to reduce the amount of disturbed meta
20、l created, in part,from frictional heat during this phase of preparation. The original microstructure of a specimen may also be radically altered, (atleast superficially, on the cut surface) due to metallurgical changes if an excessive amount of frictional heat is generated.5.2 Coarse GrindingUse a
21、120 grit silicon carbide (SiC) wet-belt or disk grinder and light contact pressure to obtain a planesurface free from deep grooves. In addition to producing a flat surface, this procedure removes burred edges or other mechanicaldamage which may have occurred during sectioning.5.3 MountingTo ensure f
22、latness, and facilitate handling, it is recommended that specimens be mounted in phenolic, acrylicor cold-setting epoxy resins. Epoxy resins involve the blending of a liquid or powder resin in a suitable hardener to initiate anexothermic reaction to promote hardening and curing at room temperature.
23、This usually requires an overnight operation. However,an advantage of epoxy is that the mount is semitransparent and permits observation of all sides of the specimen during each phaseof the preparation. (The advantages and use of acrylic mounting resin are similar to epoxy.) Compression molding tech
24、niques maybe used with phenolic powders to produce the standard 31.7-mm (1-in.) diameter mounts. Phenolic mounts are convenient whentime constraints do not permit an overnight cold-setting operation.5.4 Fine Grinding and PolishingRotating discs flushed with running water are recommended with success
25、ively finer gritpapers of 220, 320, 400, and 600 grit SiC. (Alight to medium amount of pressure is exerted on the specimen to minimize the depthof deformation). Best results are obtained on the 600 SiC paper by grinding the specimen twice. Specimens shall be rotated 90degrees after each step until t
26、he abrasive scratches from the preceding grit have been removed. In each step, the grinding time shallbe increased to twice as long as that required to remove previous scratches. This ensures removal of disturbed metal from theprevious step. Considerable care shall be used in the fine grinding stage
27、 to prevent the formation of artifacts. See Guide E3 forautomated method.3 Manning, Paul E., Ph.D., Metallographic Preparation of 686 Etching Specimens, Haynes International, Inc., Kokomo, IN, 2011.FIG. 1 Method of Designing Location of Area Shown in Photomicrograph (Guide E3)G209 1325.5 Rough Polis
28、hingThe specimen shall be washed and, preferably, ultrasonically cleaned to ensure the complete removal ofsilicon carbide carryover from the fine grinding stage. A napless type cloth shall be charged with 9-m diamond paste, and watermay be used as the lubricant. The specimen is moved counter to the
29、direction of the rotating polishing wheel from the center tothe outer periphery around the entire lapping surface. Heavy pressure is used with diamond abrasive techniques to gain themaximum cutting rate. At the conclusion of this stage, the specimen shall again be cleaned to remove any diamond polis
30、hingresidue remaining in pinholes, cracks, and cavities.5.6 Vibrator Polishing:5.6.1 Semi-final and final polishing operations on a major portion of metallographic specimens may be completed on vibratorypolishing units. A nylon polishing cloth using a slurry of 30 g of 0.3 m alumina polishing abrasi
31、ve and 500 mL of distilled ordeionized water are recommended for this operation. Additional weight in the form of a stainless steel cap must be placed on thespecimen. The suggested weight to achieve a satisfactory polish in 30-60 min on a 31.7 mm (1-in.) diameter mount is 350 g.5.6.2 Other methods o
32、f final polishing may be utilized, for example using a manual or automatic polishing wheel with fine (3m) abrasive polishing compound.NOTE 1For a more extensive description of various metallographic techniques, refer to Samuels, Petzow, and VanderVoort.45.6.2 Samples shall be cleaned with a cotton s
33、wab under running water to remove the alumina particle film, placed on a shortnap micro-cloth with a slurry of 30 g of 0.05 m alumina abrasive and 500 mL of distilled water, and polished until a scratch-freesurface is obtained. Again a 350-g weight is used to augment polishing. Specimens usually req
34、uire 25 to 30 min to produce asatisfactory final polish. The specimen can usually be polished an additional 10 to 15 min without producing harmfulover-polishing effects, but too much time may create relief on samples which are narrow across the polished surface.5.6.3 Other methods of final polishing
35、 may be utilized, for example using a manual or automatic polishing wheel with fine (3m) abrasive polishing compound.NOTE 1For a more extensive description of various metallographic techniques, refer to Samuels, Petzow, and VanderVoort.45.7 Surface Preparation:5.7.1 The surface, prior to etching, sh
36、all:5.7.1.1 Be free from scratches, stains, and other imperfections which mar the surface,5.7.1.2 Retain all non-metallic inclusions intact, and5.7.1.3 Not exhibit any appreciable relief effect between micro-constituents.5.8 Electrolytic Etching Procedures:5.8.1 Structural components of an alloy are
37、 revealed during etching by a preferential attack or staining of the variousconstituents by the reagents. This is due to differences in the chemical composition of the phases and attending rates of solution.Immediately prior to etching, specimens shall be lightly polished (using 0.05 m or equivalent
38、 substitute) and swabbed with cottonunder running water to remove any air-formed oxide film, to reduce chances of staining.5.8.2 Place the specimen immersed face up in the etching reagent. The cathode is placed approximately one inch from thespecimen, and the anode is put in contact with the sample.
39、 During etching, the cathode is moved to assure a uniform action of theetching reagent on the specimen. The sample is then washed and repolished lightly, if needed, to remove any traces of disturbedmetal on the surface, and then re-etched.5.8.3 Etchant:5.8.3.1 Option A10 % chromic acid in Specificat
40、ion D1193 water.5.8.3.2 Option B5 g oxalic acid mixed with 95 mL HCl (reagent grade).NOTE 2Some experimentation may be required to determine if the Option A or if the Option B etchant is more applicable for a specific application.5.8.4 Etching Parameters:5.8.4.1 Electrolytic6 volts DC.5.8.4.2 Cathod
41、e, Carbon or Stainless Steel may be used.5.8.4.3 Stainless anode probe.5.8.5 Etching Time:5.8.5.1 Option A1 to 5 s, depending on heat treated condition and size of sample.5.8.5.2 Option B20 to 25 s, depending on heat treated condition and size of sample.5.8.6 Sample Polishing:5.8.6.1 The sample must
42、 have a fresh polish. If the surface has been dry, even for a few seconds, give the sample 6 to 10 lapson soft nylon-type cloth with 0.05 m alumina final polishing compound, then place directly under running water and swab witha cotton pad. The sample surface must be kept wet.5.8.6.2 Place sample fa
43、ce up in etchant. With good overhead light to visually see sample surface: make contact at end or cornerof sample with anode probe or wire lead tacked to the back of the specimen, dip carbon cathode into etchant, watch to see any4 Samuels, L. E., Metallographic Polishing by Mechanical Methods, Ameri
44、can Society for Metals (ASM), Metals Park, OH, 3rd Ed., 1982; Petzow, G., MetallographicEtching, ASM, 1978; and VanderVoort, G., Metallography: Principles and Practice, McGraw Hill, NY, 2nd Ed., 1999.G209 133surface change, and break contact when finished. Before removing sample from etchant, agitat
45、e it to remove any film on surface.Pull sample and put it under running water. Rinse with methanol, then place sample under forced hot air dryer until it is thoroughlydry.5.8.6.3 If etch is too light and needs to be heavier, do not take sample back to running water and then into etchant. Instead, it
46、must go back to the final cloth for 6 to 10 laps making sure that no part of surface dries; failure to do this can, and most likelywill, result in staining. If the sample does stain do not try to remove stain on final cloth. Rather, go back to the papers (at leastto the 400 and 600 grit), then 5 to
47、9 m diamond and then to 0.05 m alumina, again, keeping sample surface wet. Repeat asdescribed before.NOTE 3The use of either 3 m diamond or 0.3 m alumina in the polishing procedure in 5.8.6.3 may result in scratches remaining on the polishedsurface of the mounted specimen.6. Examination and Evaluati
48、on6.1 A visual examination and photographic reproduction of specimen surface is compared to photomicrographs in Fig. 2 (a ton) and Fig. 3 (a to j) for microstructures exhibiting the absence and presence, respectively, of significant mu phase.Amagnificationof 200 shall be used for metallographic eval
49、uation. If any of the evaluated triplicate test specimens are considered rejectable forthe presence of mu phase, the tested material shall be considered rejectable.6.2 Microstructures shown in Fig. 2 (a to n) are considered Acceptable, reflecting the absence of significant mu phase.6.3 Microstructures shown in Fig. 3 (a to j) are considered Rejectable, reflecting the presence of significant mu phase.7. Report7.1 The specimen size, source, and identification.7.2 The test sample orientation per Fig. 1.7.3 The etching procedure: Electrochemical (O
