ASTM E1077-14(2021)
(Test Method)Standard Test Methods for Estimating the Depth of Decarburization of Steel Specimens
Standard Test Methods for Estimating the Depth of Decarburization of Steel Specimens
SIGNIFICANCE AND USE
5.1 These test methods are used to detect surface losses in carbon content due to heating at elevated temperatures, as in hot working or heat treatment.
5.2 Results of such tests may be used to qualify material for shipment according to agreed upon guidelines between purchaser and manufacturer, for guidance as to machining allowances, or to assess the influence of processing upon decarburization tendency.
5.3 Screening tests are simple, fast, low-cost tests designed to separate non-decarburized samples from those with appreciable decarburization. Based on the results of such tests, the other procedures may be utilized as applicable.
5.4 Microscopical tests require a metallographically polished cross section to permit reasonably accurate determination of the depth and nature of the decarburization present. Several methods may be employed for estimation of the depth of decarburization. The statistical accuracy of each varies with the amount of effort expended.
5.5 Microindentation hardness methods are employed on polished cross sections and are most suitable for hardened specimens with reasonably uniform microstructures. This procedure can be used to define the depth to a specific minimum hardness or the depth to a uniform hardness.
5.6 Chemical analytical methods are limited to specimens with simple, uniform shapes and are based on analysis of incremental turnings or after milling at fixed increments.
5.7 Microscopical tests are generally satisfactory for determining the suitability of material for intended use, specification acceptance, manufacturing control, development, or research.
SCOPE
1.1 These test methods cover procedures for estimating the depth of decarburization of steels irrespective of the composition, matrix microstructure, or section shape. The following basic procedures may be used:
1.1.1 Screening methods.
1.1.2 Microscopical methods.
1.1.3 Microindentation hardness methods.
1.1.4 Chemical analysis methods.
1.2 In case of a dispute, the rigorous quantitative or lineal analysis method (see 7.3.5 and 7.3.6) shall be the referee method. These methods can be employed with any cross-sectional shape. The chemical analytical methods generally reveal a greater depth of decarburization than the microscopical methods but are limited to certain simple shapes and by availability of equipment. These techniques are generally reserved for research studies. The microindentation hardness method is suitable for accurate measurements of hardened structures with relatively homogeneous microstructures.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 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.
General Information
Relations
Standards Content (Sample)
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: E1077 − 14 (Reapproved 2021)
Standard Test Methods for
Estimating the Depth of Decarburization of Steel
Specimens
This standard is issued under the fixed designation E1077; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
INTRODUCTION
These test methods may be used to estimate the average or greatest depth of decarburization in
hardened or non-hardened steel products. The test methods described range from simple screening
tests to more statistically rigorous test methods depending upon the needs of the investigation.
1. Scope 1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 These test methods cover procedures for estimating the
ization established in the Decision on Principles for the
depth of decarburization of steels irrespective of the
Development of International Standards, Guides and Recom-
composition, matrix microstructure, or section shape. The
mendations issued by the World Trade Organization Technical
following basic procedures may be used:
Barriers to Trade (TBT) Committee.
1.1.1 Screening methods.
1.1.2 Microscopical methods.
2. Referenced Documents
1.1.3 Microindentation hardness methods.
2.1 ASTM Standards:
1.1.4 Chemical analysis methods.
A941TerminologyRelatingtoSteel,StainlessSteel,Related
1.2 In case of a dispute, the rigorous quantitative or lineal
Alloys, and Ferroalloys
analysis method (see 7.3.5 and 7.3.6) shall be the referee
E3Guide for Preparation of Metallographic Specimens
method. These methods can be employed with any cross-
E7Terminology Relating to Metallography
sectional shape. The chemical analytical methods generally
E340Practice for Macroetching Metals and Alloys
reveal a greater depth of decarburization than the microscopi-
E350Test Methods for Chemical Analysis of Carbon Steel,
cal methods but are limited to certain simple shapes and by
Low-Alloy Steel, Silicon Electrical Steel, Ingot Iron, and
availability of equipment. These techniques are generally
Wrought Iron
reserved for research studies. The microindentation hardness
E384Test Method for Microindentation Hardness of Mate-
method is suitable for accurate measurements of hardened
rials
structures with relatively homogeneous microstructures.
E407Practice for Microetching Metals and Alloys
1.3 The values stated in SI units are to be regarded as
E415Test Method for Analysis of Carbon and Low-Alloy
standard. No other units of measurement are included in this
Steel by Spark Atomic Emission Spectrometry
standard.
E1951Guide for Calibrating Reticles and Light Microscope
Magnifications
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3. Terminology
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
3.1 Definitions:
mine the applicability of regulatory limitations prior to use.
3.1.1 Fordefinitionsoftermsusedinthesetestmethods,see
Terminology E7 and Terminology A941.
3.2 Definitions of Terms Specific to This Standard:
These test methods are under the jurisdiction of ASTM Committee E04 on
Metallography and are the direct responsibility of Subcommittee E04.14 on
Quantitative Metallography. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved June 1, 2021. Published June 2021. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1985. Last previous edition approved in 2014 as E1077–14. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E1077-14R21. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1077 − 14 (2021)
3.2.1 average depth of decarburization—the mean value of cedure can be used to define the depth to a specific minimum
five or more measurements of the total depth of decarburiza- hardness or the depth to a uniform hardness.
tion.
5.6 Chemical analytical methods are limited to specimens
3.2.2 average free-ferrite depth—the mean value of five or
with simple, uniform shapes and are based on analysis of
more measurements of the depth of complete decarburization.
incremental turnings or after milling at fixed increments.
3.2.3 complete decarburization—loss of carbon content at
5.7 Microscopical tests are generally satisfactory for deter-
the surface of a steel specimen to a level below the solubility
miningthesuitabilityofmaterialforintendeduse,specification
limit of carbon in ferrite so that only ferrite is present.
acceptance, manufacturing control, development, or research.
3.2.4 free-ferrite depth—theperpendiculardistancefromthe
6. Sampling
surface of the specimen to that location where the structure is
no longer fully ferritic, that is, other transformation products 6.1 Samples should be taken at locations that are represen-
tative of the bulk specimen. The location and number of
are observed.
samplestakendependsonthenatureofthematerialtobetested
NOTE 1—The term free ferrite has also been used to describe globular,
and will be defined upon agreements between manufacturer
isolated grains of proeutectoid ferrite in the microstructure of medium-
and purchaser.
carbon hypoeutectoid steels.
3.2.5 maximum depth of decarburization—the largest mea-
6.2 Specimens for screening tests using bulk hardness tests,
sured value of the total depth of decarburization.
such as the Rockwell test, should be small enough so that they
can be properly supported on the anvil of the tester. The
3.2.6 partial decarburization—loss of carbon content at the
specimen surface should not be altered except for scale
surface of a steel specimen to a level less than the bulk carbon
removal (if present) using a method that will not alter the
content of the unaffected interior but greater than the room
subsurface metal.
temperature solubility limit of carbon in ferrite.
6.3 Specimens for the microscopical methods or for micro-
3.2.7 total depth of decarburization—the perpendicular dis-
indentation hardness tests or for macroscopic screening meth-
tance from the specimen surface to that location in the interior
ods should be cut from the bulk specimen perpendicular to the
wherethebulkcarboncontentisreached;thatis,thesumofthe
longitudinalaxisoftheproductsothatmeasurementsaremade
depths of complete and partial decarburization.
on a transverse plane.This procedure permits determination of
4. Summary of Test Method
the variation of decarburization around the periphery of the
specimen.
4.1 Thesetestmethodsaredesignedtodetectchangesinthe
6.3.1 For specimens up to about 2.5-cm diameter, the entire
microstructure, hardness, or carbon content at the surface of
steel sections due to decarburization. The depth of decarbur- cross section is polished and examined. For larger cross
sections, one or more specimens shall be prepared to assess
ization is determined as the depth where a uniform
microstructure, hardness, or carbon content, typical of the variations in surface decarburization. Figs. 1-3 show examples
of typical sampling schemes that may be used for larger
interior of the specimen, is observed.
sections; the sampling scheme for large sections should be
5. Significance and Use
determined upon mutual agreement between manufacturer and
5.1 These test methods are used to detect surface losses in purchaser.
carbon content due to heating at elevated temperatures, as in
6.4 Specimens for chemical analytical methods must be of
hot working or heat treatment.
sufficient length so that the weight of incremental turnings is
5.2 Resultsofsuchtestsmaybeusedtoqualifymaterialfor adequate for chemical analysis or the size of milled surfaces is
large enough for sparking yet small enough to fit in the
shipment according to agreed upon guidelines between pur-
chaser and manufacturer, for guidance as to machining specimen holder.
allowances, or to assess the influence of processing upon
7. Procedure
decarburization tendency.
7.1 Screening Methods:
5.3 Screening tests are simple, fast, low-cost tests designed
7.1.1 BulkSurfaceHardness—Forhardenedspecimens,par-
to separate non-decarburized samples from those with appre-
ticularly those in the as-quenched condition, a short section of
ciable decarburization. Based on the results of such tests, the
the material to be heat treated is cut and heat treated in the
other procedures may be utilized as applicable.
same manner, or along with, the material of interest. The test
5.4 Microscopical tests require a metallographically pol-
specimen,howeverisnottempered.Anyscaleonthetestpiece
ishedcrosssectiontopermitreasonablyaccuratedetermination
is removed by wire brushing, glass-bead blasting, etc., and
of the depth and nature of the decarburization present. Several
hardness tested, usually with the Rockwell C scale. The
methods may be employed for estimation of the depth of
presence of decarburization is indicated by the difference
decarburization.Thestatisticalaccuracyofeachvarieswiththe
between the surface hardness and the theoretical maximum
amount of effort expended.
hardness for the carbon content of the steel. This method is
5.5 Microindentation hardness methods are employed on most suitable for those steels with bulk carbon contents below
polished cross sections and are most suitable for hardened about 0.55% carbon but will detect gross decarburization in
specimens with reasonably uniform microstructures. This pro- steels with higher bulk carbon contents. The method is not
E1077 − 14 (2021)
FIG. 1 Typical Sampling Schemes for Round Bars of Different Size
suitable for steels that cannot be quench-hardened, for between the free-ferrite layer, when present, and the interior
example, low-carbon steels. structure. The depth of partial decarburization can best be
7.1.2 Macroscopical Etch Appearance—The presence of assessed when this zone contains ferrite and pearlite. If the
decarburization is indicated by a difference in etching contrast specimen has been spheroidized, the variation in carbide
between the surface and the interior of the specimen. A content in the partially decarburized zone is used to assess the
transverse section can be ground and macroetched or polished total depth of decarburization. For heat-treated specimens, the
and microetched. The method is suitable for as-rolled, as-
presence of non-martensitic structures in the partially decar-
forged, annealed, normalized, or heat-treated specimens. The
burized zone is used to estimate the total depth of decarbur-
decarburized surface layer, if present, usually exhibits a light-
ization. Such measurements will generally underestimate the
etching appearance. Suitable macroetchants are listed in Test
total depth of decarburization. For certain highalloy
Method E340.
spheroidize-annealed tool steels, the depth of decarburization
can be estimated by changes in the etch color. For austenitic
7.2 Microscopical Methods:
manganese steels in the solution-annealed condition, depths
7.2.1 Microscopical methods are most suitable for measur-
corresponding to certain carbon contents can be defined by
ing the depth of decarburization of as-hot rolled, as-forged,
changes in the microstructure due to decarburization. Ex-
annealed,ornormalizedspecimens.Thesemethodscanalsobe
amples of decarburization for as-rolled, heat treated, and
applied to heat-treated specimens, although with less certainty
spheroidize-annealed steels are shown in Figs. 4-9, respec-
in determining the maximum affected depth. Spheroidize-
tively.
annealedorcold-workedspecimenscanalsobeevaluated;but,
7.2.3 Specimen polishing must be conducted in a manner
detectionofstructuralvariationsduetodecarburizationismore
difficult than with hot-worked or fully annealed structures. that does not produce edge rounding. Unmounted, unprotected
7.2.2 Measurement of the depth of decarburization is based specimens can be satisfactorily prepared using certain auto-
on evaluation of the variation in microstructure at the surface matic polishing devices. Low-nap cloths should be employed;
due to the change in carbon content. The depth of complete polishing with abrasives finer than 1-µm diamond is often
decarburizationiseasiesttoassessduetotheexcellentcontrast unnecessary. When such devices are not available, or when
E1077 − 14 (2021)
FIG. 2 Typical Sampling Schemes for Square Bars of Different Size
specimens are small or of an inconvenient shape for such etchantscanbeusedifdictatedbythesituationencountered.In
devices, specimens should be mounted in clamps or in various such cases, agreement should be obtained between manufac-
plastic media. With some mounting media, edge preservation
turer and purchaser.
may be inadequate. The compression mounting epoxy materi-
7.2.5 For solution-annealed austenitic manganese steels,
als generally provide the best edge retention of the commonly
epsilon martensite will be present in the surface region where
available plastics. Electrolytic or electroless plating provides
the carbon content is below about 0.5% carbon.This structure
optimum edge retention and is recommended for critical work.
is best revealed by etching first with 2% nital for 5 s and then
Polishing must be practiced using techniques that produce a
with20%aqueoussodiummetabisulphiteforabout20s.After
true representation of the surface microstructure, as described
measurement of the depth of this layer, the specimen can be
in Guide E3.
aged at about 560°C for1hto precipitate pearlite at the grain
7.2.4 Etching should be conducted using standard etchants,
boundaries in the core region where the carbon content is
(see Test Methods E407) such as nital or picral, based on the
experience of the rater with the material being tested. Special
E1077 − 14 (2021)
FIG. 3 Typical Sampling Schemes for Flat and Rectangular Bars of Different Size
FIG. 4 Example of an As-Rolled, Fully Pearlitic Alloy Steel Microstructure With No Apparent Decarburization. Dark Layer at Surface Is
Iron Oxide (Mill Scale) (200×, 2 % Nital Etch)
above 1.16%. Etching with nital or picral will
...
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