ASTM G209-14(2022)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: G209 − 14 (Reapproved 2022)
Standard Practice for
Detecting mu-phase in Wrought Nickel-Rich, Chromium,
Molybdenum-Bearing Alloys
This standard is issued under the fixed designation G209; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This practice incorporates etching and metallographic 2.1 ASTM Standards:
examination of Wrought Nickel-Rich, Chromium, D1193Specification for Reagent Water
Molybdenum-BearingAlloys such as, but not limited to, UNS E3Guide for Preparation of Metallographic Specimens
N06686 and UNS N10276. E7Terminology Relating to Metallography
E1245Practice for Determining the Inclusion or Second-
1.2 Microstructures have a strong influence on properties
Phase Constituent Content of Metals byAutomatic Image
and successful application of metals and alloys. The presence
Analysis
ofmu-phaseinthemicrostructuremaysignificantlyreducethe
E1268Practice for Assessing the Degree of Banding or
corrosion resistance of Wrought Nickel-Rich, Chromium, and
Orientation of Microstructures
Molybdenum-Bearing Alloys.
G193Terminology and Acronyms Relating to Corrosion
1.3 This practice may be used to determine the presence of
mu-phase in Wrought Nickel-Rich, Chromium, and 3. Terminology
Molybdenum-Bearing Alloys through comparison of micro-
3.1 Definitions:
structure observed for etched metallographic specimens to a
3.1.1 The terminology used herein, if not specifically de-
glossary of photomicrographs displaying the presence and
fined otherwise, shall be in accordance with Terminology
absence of mu-phase in the microstructure.
G193. Definitions provided herein and not given in Terminol-
1.4 The values stated in SI units are to be regarded as ogy G193 are limited only to this practice.
standard. The values given in parentheses after SI units are 3.1.2 For metallographic definitions used in this practice,
providedforinformationonlyandarenotconsideredstandard. refer to Terminology E7.
3.1.3 For evaluation of inclusions, secondary phases and
1.5 This standard does not purport to address all of the
banding, if desired, refer to Practices E1245 and E1268.
safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.2.1 mu-phase (µ), n—rhombohedral phase which may
priate safety, health, and environmental practices and deter-
occur in Nickel-Rich, Chromium, Molybdenum-Bearing Al-
mine the applicability of regulatory limitations prior to use.
loysandmayoccurascoarse,irregularplatelets,whichformat
1.6 This international standard was developed in accor-
high temperature.
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
4. Significance and Use
Development of International Standards, Guides and Recom-
4.1 These test methods describe laboratory tests to deter-
mendations issued by the World Trade Organization Technical
mine the presence of mu-phase in Wrought Nickel-Rich,
Barriers to Trade (TBT) Committee.
Chromium, and Molybdenum-Bearing Alloys through com-
parison of microstructure observed for etched metallographic
This practice is under the jurisdiction ofASTM Committee G01 on Corrosion
of Metals and is the direct responsibility of Subcommittee G01.05 on Laboratory
Corrosion Tests. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2022. Published October 2022. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2012. Last previous edition approved in 2018 as G209–14 (2018). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/G0209-14R22. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G209 − 14 (2022)
5.2 Coarse Grinding—Use a 120 grit silicon carbide (SiC)
wet-belt or disk grinder and light contact pressure to obtain a
plane surface free from deep grooves. In addition to producing
a flat surface, this procedure removes burred edges or other
mechanical damage which may have occurred during section-
ing.
5.3 Mounting—Toensureflatness,andfacilitatehandling,it
is recommended that specimens be mounted in phenolic,
acrylic or cold-setting epoxy resins. Epoxy resins involve the
blending of a liquid or powder resin in a suitable hardener to
initiate an exothermic reaction to promote hardening and
curing at room temperature.This usually requires an overnight
operation.However,anadvantageofepoxyisthatthemountis
semitransparent and permits observation of all sides of the
specimen during each phase of the preparation. (The advan-
tages and use of acrylic mounting resin are similar to epoxy.)
Compression molding techniques may be used with phenolic
powders to produce the standard 31.7mm (1 ⁄4in.) diameter
mounts.Phenolicmountsareconvenientwhentimeconstraints
FIG. 1 Method of Designing Location of Area Shown in Photomi-
crograph (Guide E3) do not permit an overnight cold-setting operation.
5.4 Fine Grinding and Polishing—Rotating discs flushed
with running water are recommended with successively finer
specimens to a glossary of photomicrographs displaying the grit papers of 220grit, 320grit, 400grit, and 600 grit SiC. (A
presence and absence of mu-phase in the microstructure. The lighttomediumamountofpressureisexertedonthespecimen
presence of mu-phase in the microstructure may significantly to minimize the depth of deformation). Best results are
reduce the corrosion resistance, strength, toughness and duc- obtainedonthe600SiCpaperbygrindingthespecimentwice.
tility of Wrought Nickel-Rich, Chromium, and Molybdenum- Specimens shall be rotated 90 degrees after each step until the
Bearing Alloys. abrasive scratches from the preceding grit have been removed.
In each step, the grinding time shall be increased to twice as
5. Sample Preparation and Etching
long as that required to remove previous scratches. This
ensures removal of disturbed metal from the previous step.
5.1 Sectioning:
Considerable care shall be used in the fine grinding stage to
5.1.1 The selection of test specimens for metallographic
prevent the formation of artifacts. See Guide E3 for automated
examination is extremely important because, if their interpre-
method.
tationistobeofvalue,thespecimensmustberepresentativeof
the material that is being studied and shall be per location E
5.5 Rough Polishing—The specimen shall be washed and,
(longitudinal section perpendicular to rolled surface) for plate
preferably, ultrasonically cleaned to ensure the complete re-
and sheet and per location G (radial longitudinal section) for
movalofsiliconcarbidecarryoverfromthefinegrindingstage.
rod and bar per Fig. 1 (Guide E3).The intent or purpose of the
Anaplesstypeclothshallbechargedwith9µmdiamondpaste,
metallographic examination will usually dictate the location of
andwatermaybeusedasthelubricant.Thespecimenismoved
the specimens to be studied. For rod and bar test specimens
countertothedirectionoftherotatingpolishingwheelfromthe
specifically, samples are taken from location G as seen in Fig.
center to the outer periphery around the entire lapping surface.
1. Triplicate test specimens shall be evaluated for determina-
Heavy pressure is used with diamond abrasive techniques to
tion of the presence of mu-phase.
gainthemaximumcuttingrate.Attheconclusionofthisstage,
5.1.2 Cut the specimen to a convenient size using any of
the specimen shall again be cleaned to remove any diamond
various types of silicon carbide, diamond, boron carbide or
polishing residue remaining in pinholes, cracks, and cavities.
other carbide cutoff blades. Deformation damage can be
5.6 Polishing:
minimized by using thin cutoff wheels 0.78 mm ( ⁄32 in.) thick
5.6.1 Semi-final and final polishing operations on a major
asopposedto1.58mm( ⁄16in.).Nevercutdry.Useofadequate
portion of metallographic specimens may be completed on
water coolant is desired to reduce the amount of disturbed
vibratorypolishingunits.Anylonpolishingclothusingaslurry
metal created, in part, from frictional heat during this phase of
of 30 g of 0.3 µm alumina polishing abrasive and 500 mL of
preparation. The original microstructure of a specimen may
distilled or deionized water are recommended for this opera-
also be radically altered, (at least superficially, on the cut
tion.Additionalweightintheformofastainlesssteelcapmust
surface)duetometallurgicalchangesifanexcessiveamountof
be placed on the specimen. The suggested weight to achieve a
frictional heat is generated.
satisfactory polish in 30min to 60min on a 31.7mm (1¼in.)
diameter mount is 350 g.
5.6.2 S
...