Standard Test Method for Galling Resistance of Materials

SIGNIFICANCE AND USE
5.1 This test method is designed to rank material couples in their resistance to the failure mode caused by galling and not merely to classify the surface appearance of sliding surfaces.  
5.2 This test method should be considered when damaged (galled) surfaces render components non-serviceable. Experience has shown that galling is most prevalent in sliding systems that are slow moving and operate intermittently. The galling and seizure of threaded components is a classic example which this test method most closely simulates.  
5.3 Other galling-prone examples include: sealing surfaces of value trim which may leak excessively due to galling; and pump wear rings that may function ineffectively due to galling.  
5.4 If the equipment continues to operate satisfactorily and loses dimension gradually, then mechanical wear should be evaluated by a different test such as the crossed cylinder Test Method (see Test Method G83). Chain belt pins and bushings are examples of this type of problem.  
5.5 This test method should not be used for quantitative or final design purposes since many environmental factors influence the galling performance of materials in service. Lubrication, alignment, stiffness and geometry are only some of the factors that can affect how materials perform. This test method has proven valuable in screening materials for prototypical testing that more closely simulates actual service conditions.
SCOPE
1.1 This test method covers a laboratory test which ranks the galling resistance of material couples. Most galling studies have been conducted on bare metals and alloys; however, non-metallics, coatings, and surface modified alloys may also be evaluated by this test method.  
1.2 This test method is not designed for evaluating the galling resistance of material couples sliding under lubricated conditions because galling usually will not occur under lubricated sliding conditions using this test method.  
1.3 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.  
1.4 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

Status
Published
Publication Date
31-Oct-2023
Technical Committee
Drafting Committee
Current Stage
Ref Project

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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: G98 − 23
Standard Test Method for
1
Galling Resistance of Materials
This standard is issued under the fixed designation G98; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This test method covers a laboratory test which ranks 3.1 Definitions: Terminology Relating to Wear and Erosion
the galling resistance of material couples. Most galling studies G40:
have been conducted on bare metals and alloys; however, 3.1.1 galling—a form of surface damage arising between
non-metallics, coatings, and surface modified alloys may also sliding solids, distinguished by macroscopic, usually localized,
be evaluated by this test method. roughening and creation of protrusions above the original
surface; it often includes plastic flow or material transfer, or
1.2 This test method is not designed for evaluating the
both.
galling resistance of material couples sliding under lubricated
conditions because galling usually will not occur under lubri- 3.2 Definitions of Terms Specific to This Standard:
cated sliding conditions using this test method. 3.2.1 threshold galling stress—the stress midway between
the highest non-galled stress and the lowest galled stress as
1.3 This standard does not purport to address all of the
determined by this test method.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Summary of Test Method
priate safety, health, and environmental practices and deter-
4.1 This test method uses available laboratory equipment
mine the applicability of regulatory limitations prior to use.
capable of maintaining a constant, compressive load between
1.4 This international standard was developed in accor-
two flat specimens, such as hydraulic or screw feed compres-
dance with internationally recognized principles on standard-
sion testing machines. One specimen is slowly rotated one
ization established in the Decision on Principles for the
revolution 360° relative to the other specimen. The surfaces are
Development of International Standards, Guides and Recom-
examined for galling after sliding. The criterion for whether
mendations issued by the World Trade Organization Technical
galling occurs is the appearance of the specimens based on
Barriers to Trade (TBT) Committee.
unassisted visual examination. If the specimens have not
galled, a new set of specimens is tested at increased load. This
2. Referenced Documents
process is continued until galling occurs.
2
2.1 ASTM Standards:
4.2 Appropriate load intervals are chosen to determine the
E177 Practice for Use of the Terms Precision and Bias in
threshold galling stress within an acceptable range.
ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to
4.3 The higher the threshold galling stressing, the more
Determine the Precision of a Test Method
galling resistant is the test couple.
G40 Terminology Relating to Wear and Erosion
5. Significance and Use
G83 Test Method for Wear Testing with a Crossed-Cylinder
3
Apparatus (Withdrawn 2005)
5.1 This test method is designed to rank material couples in
their resistance to the failure mode caused by galling and not
merely to classify the surface appearance of sliding surfaces.
1
This test method is under the jurisdiction of ASTM Committee G02 on Wear
5.2 This test method should be considered when damaged
and Erosion and is the direct responsibility of Subcommittee G02.40 on Non-
(galled) surfaces render components non-serviceable. Experi-
Abrasive Wear.
ence has shown that galling is most prevalent in sliding
Current edition approved Nov. 1, 2023. Published November 2023. Originally
approved in 1989. Last previous edition approved in 2022 as G98 – 17 (2022). DOI:
systems that are slow moving and operate intermittently. The
10.1520/G0098-23.
galling and seizure of threaded components is a classic
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
example which this test method most closely simulates.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
5.3 Other galling-prone examples include: sealing surfaces
the ASTM website.
3
of value trim which may leak excessively due to galling; and
The last approved version of this historical standard is referenced on
www.astm.org. pump wear rings that may function ineffectivel
...

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. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: G98 − 17 (Reapproved 2022) G98 − 23
Standard Test Method for
1
Galling Resistance of Materials
This standard is issued under the fixed designation G98; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers a laboratory test which ranks the galling resistance of material couples. Most galling studies have been
conducted on bare metals and alloys; however, non-metallics, coatings, and surface modified alloys may also be evaluated by this
test method.
1.2 This test method is not designed for evaluating the galling resistance of material couples sliding under lubricated conditions
because galling usually will not occur under lubricated sliding conditions using this test method.
1.3 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.
1.4 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.
2. Referenced Documents
2
2.1 ASTM Standards:
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
G40 Terminology Relating to Wear and Erosion
3
G83 Test Method for Wear Testing with a Crossed-Cylinder Apparatus (Withdrawn 2005)
3. Terminology
3.1 Definitions: Terminology Relating to Wear and Erosion G40:
3.1.1 galling—a form of surface damage arising between sliding solids, distinguished by macroscopic, usually localized,
roughening and creation of protrusions above the original surface; it often includes plastic flow or material transfer, or both.
3.1.1.1 Discussion—
The onset of galling usually requires that the contact pressure exceeds some threshold value. Galling can be a precursor to seizing
or loss of function. The identification of galling is somewhat subjective, and complete agreement does not exist, even among
experts.
3.2 Definitions of Terms Specific to This Standard:
1
This test method is under the jurisdiction of ASTM Committee G02 on Wear and Erosion and is the direct responsibility of Subcommittee G02.40 on Non-Abrasive Wear.
Current edition approved Nov. 1, 2022Nov. 1, 2023. Published November 2022November 2023. Originally approved in 1989. Last previous edition approved in 20172022
as G98 – 17.G98 – 17 (2022). DOI: 10.1520/G0098-17R22.10.1520/G0098-23.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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G98 − 23
3.2.1 threshold galling stress—the stress midway between the highest non-galled stress and the lowest galled stress as determined
by this test method.
4. Summary of Test Method
4.1 This test method uses available laboratory equipment capable of maintaining a constant, compressive load between two flat
specimens, such as hydraulic or screw feed compression testing machines. One specimen is slowly rotated one revolution 360°
relative to the other specimen. The surfaces are examined for galling after sliding. The criterion for whether galling occurs is the
appearance of the specimens based on unassisted visual examination. If the specimens have not galled, a new set of specimens is
tested at increased load. This process is continued until galling occurs.
4.2 Appropriate load intervals are chosen to determine the threshold galling stress within an acceptable range.
4.3 The higher the threshold galling stressing, the more galling resistant is the test couple.
5. Significance and Use
5.1 This test method is designed to
...

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