Standard Test Methods for Determining Area Percentage Porosity in Thermal Sprayed Coatings

SIGNIFICANCE AND USE
4.1 TSCs are susceptible to the formation of porosity due to a lack of fusion between sprayed particles or the expansion of gases generated during the spraying process. The determination of area percent porosity is important in order to monitor the effect of variable spray parameters and the suitability of a coating for its intended purpose. Depending on application, some or none of this porosity may be tolerable.  
4.2 These test methods cover the determination of the area percentage porosity of TSCs. Method A is a manual, direct comparison method utilizing the seven standard images in Figs. 1-7 which depict typical distributions of porosity in TSCs. Method B is an automated technique requiring the use of a computerized image analyzer.
FIG. 1 — 0.5 % Porosity  
FIG. 2 — 1.0 % Porosity  
FIG. 3 — 2.0 % Porosity  
FIG. 4 — 5.0 % Porosity  
FIG. 5 — 8.0 % Porosity  
FIG. 6 — 10.0 % Porosity  
FIG. 7 — 15.0 % Porosity  
4.3 These methods quantify area percent porosity only on the basis of light reflectivity from a metallographically polished cross section. See Guide E1920 for recommended metallographic preparation procedures.  
4.4 The person using these test methods must be familiar with the visual features of TSCs and be able to determine differences between inherent porosity and oxides. The individual must be aware of the possible types of artifacts that may be created during sectioning and specimen preparation, for example, pullouts and smearing, so that results are reported only on properly prepared specimens. Examples of properly prepared specimens are shown in Figs. 8-10. If there are doubts as to the integrity of the specimen preparation it is suggested that other means be used to confirm microstructural features. This may include energy dispersive spectroscopy (EDS), wavelength dispersive spectroscopy (WDS) or cryogenic fracture of the coating followed by analysis of the fractured surfaces with a scanning electron microscope (SEM).
FIG. 8 Ni/Al T...
SCOPE
1.1 These test methods cover procedures to perform porosity ratings on metallographic specimens of thermal sprayed coatings (TSCs) prepared in accordance with Guide E1920 by direct comparison to standard images and via the use of automatic image analysis equipment.  
1.2 These test methods deal only with recommended measuring methods and nothing in them should be construed as defining or establishing limits of acceptability for any measured value of porosity.  
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.

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Publication Date
31-Aug-2021
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ASTM E2109-01(2021) - Standard Test Methods for Determining Area Percentage Porosity in Thermal Sprayed Coatings
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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: E2109 − 01 (Reapproved 2021)
Standard Test Methods for
Determining Area Percentage Porosity in Thermal Sprayed
1
Coatings
This standard is issued under the fixed designation E2109; 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 These test methods cover procedures to perform poros- 3.1 Definitions—For definitions of terms used in these test
ity ratings on metallographic specimens of thermal sprayed methods refer to Terminology E7.
coatings (TSCs) prepared in accordance with Guide E1920 by
3.2 Definitions of Terms Specific to This Standard:
direct comparison to standard images and via the use of
3.2.1 halo effect—unwanted detection of the perimeter of
automatic image analysis equipment.
one phase (due to a shared gray value at the phase boundary)
1.2 These test methods deal only with recommended mea- when setting the detection limits of another.
suring methods and nothing in them should be construed as
3.2.2 linear detachment, n—a region within a TSC in which
defining or establishing limits of acceptability for any mea-
two successively deposited splats of coating material have not
sured value of porosity.
metallurgically bonded.
1.3 This standard does not purport to address all of the
3.2.3 porosity, n—cavity type discontinuities (voids) or
safety concerns, if any, associated with its use. It is the
linear detachments within a sprayed coating.
responsibility of the user of this standard to establish appro-
3.2.4 splat, n—an individual globule of thermal sprayed
priate safety, health, and environmental practices and deter-
material that has been deposited on a substrate.
mine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accor-
4. Significance and Use
dance with internationally recognized principles on standard-
4.1 TSCs are susceptible to the formation of porosity due to
ization established in the Decision on Principles for the
a lack of fusion between sprayed particles or the expansion of
Development of International Standards, Guides and Recom-
gases generated during the spraying process. The determina-
mendations issued by the World Trade Organization Technical
tion of area percent porosity is important in order to monitor
Barriers to Trade (TBT) Committee.
the effect of variable spray parameters and the suitability of a
2. Referenced Documents
coating for its intended purpose. Depending on application,
2
2.1 ASTM Standards: some or none of this porosity may be tolerable.
E3 Guide for Preparation of Metallographic Specimens
4.2 These test methods cover the determination of the area
E7 Terminology Relating to Metallography
percentage porosity of TSCs. Method A is a manual, direct
E562 Test Method for Determining Volume Fraction by
comparison method utilizing the seven standard images in
Systematic Manual Point Count
Figs. 1-7 which depict typical distributions of porosity in
E1245 Practice for Determining the Inclusion or Second-
TSCs.MethodBisanautomatedtechniquerequiringtheuseof
Phase Constituent Content of Metals byAutomatic Image
a computerized image analyzer.
Analysis
4.3 These methods quantify area percent porosity only on
E1920 Guide for Metallographic Preparation of Thermal
the basis of light reflectivity from a metallographically pol-
Sprayed Coatings
ished cross section. See Guide E1920 for recommended
metallographic preparation procedures.
1
These test methods are under the jurisdiction of ASTM Committee E04 on
Metallography and are the direct responsibility of Subcommittee E04.14 on
4.4 The person using these test methods must be familiar
Quantitative Metallography.
with the visual features of TSCs and be able to determine
Current edition approved Sept. 1, 2021. Published November 2021. Originally
differences between inherent porosity and oxides. The indi-
approved in 2000. Last previous edition approved in 2014 as E2109 – 01(2014).
DOI: 10.1520/E2109-01R21.
vidual must be aware of the possible types of artifacts that may
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
be created during sectioning and specimen preparation, for
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
example, pullouts and smearing, so that results are reported
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. only on properly prepared specimens. Examples of properly
...

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