ASTM E1920-03
(Guide)Standard Guide for Metallographic Preparation of Thermal Sprayed Coatings
Standard Guide for Metallographic Preparation of Thermal Sprayed Coatings
SIGNIFICANCE AND USE
TSCs are used in a number of critical industrial components. TSCs can be expected to contain measurable levels of porosity and linear detachment. Accurate and consistent evaluation of specimens is essential to ensure the integrity of the coating and proper adherence to the substrate.
4.1.1 Example 1: By use of inappropriate metallographic methods, the apparent amount of porosity and linear detachment displayed by a given specimen can be increased, by excessive edge rounding, or decreased by smearing of material into voids. Therefore inaccurate levels of porosity and linear detachment will be reported even when the accuracy of the measurement technique is acceptable.
4.1.2 Example 2: Inconsistent metallographic preparation methods can cause the apparent amount of voids to vary excessively indicating a poorly controlled thermal spray process, while the use of consistent practice will regularly display the true microstructure and verify the consistency of the thermal spray process.
During the development of TSC procedures, metallographic information is necessary to validate the efficacy of a specific application.
Cross sections are usually taken perpendicular to the long axis of the specimen and prepared to reveal information concerning the following:
4.3.1 Variations in structure from surface to substrate,
4.3.2 The distribution of unmelted particles throughout the coating,
4.3.3 The distribution of linear detachment throughout the coating,
4.3.4 The distribution of porosity throughout the coating,
4.3.5 The presence of contamination within the coating,
4.3.6 The thickness of the coating (top coat and bond coat, where applicable),
4.3.7 The presence of interfacial contamination,
4.3.8 The integrity of the interface between the coating and substrate, and,
4.3.9 The integrity of the coating microstructure with respect to chemistry.
SCOPE
1.1 This guide covers recommendations for sectioning, cleaning, mounting, grinding, and polishing to reveal the microstructural features of thermal sprayed coatings (TSCs) and the substrates to which they are applied when examined microscopically. Because of the diversity of available equipment, the wide variety of coating and substrate combinations, and the sensitivity of these specimens to preparation technique, the existence of a series of recommended methods for metallographic preparation of thermal sprayed coating specimens is helpful. Adherence to this guide will provide practitioners with consistent and reproducible results. Additional information concerning standard practices for metallographic preparation can be found in Practice E3.
This standards 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:E1920–03
Standard Guide for
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Metallographic Preparation of Thermal Sprayed Coatings
This standard is issued under the fixed designation E 1920; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope a small angle to the polishing plane, such that the visible width
exhibited by the feature is expanded.
1.1 This guide covers recommendations for sectioning,
3.2.4 TSC, n—thermal sprayed coating, including, but not
cleaning, mounting, grinding, and polishing to reveal the
limited to, those formed by plasma, flame, and high velocity
microstructural features of thermal sprayed coatings (TSCs)
oxyfuel.
and the substrates to which they are applied when examined
microscopically. Because of the diversity of available equip-
4. Significance and Use
ment, the wide variety of coating and substrate combinations,
4.1 TSCs are used in a number of critical industrial compo-
and the sensitivity of these specimens to preparation technique,
nents. TSCs can be expected to contain measurable levels of
the existence of a series of recommended methods for metal-
porosity and linear detachment.Accurate and consistent evalu-
lographic preparation of thermal sprayed coating specimens is
ation of specimens is essential to ensure the integrity of the
helpful.Adherence to this guide will provide practitioners with
coating and proper adherence to the substrate.
consistent and reproducible results. Additional information
4.1.1 Example 1: By use of inappropriate metallographic
concerning standard practices for metallographic preparation
methods, the apparent amount of porosity and linear detach-
can be found in Practice E 3.
ment displayed by a given specimen can be increased, by
1.2 This standard does not purport to address all of the
excessive edge rounding, or decreased by smearing of material
safety concerns, if any, associated with its use. It is the
into voids. Therefore inaccurate levels of porosity and linear
responsibility of the user of this standard to establish appro-
detachment will be reported even when the accuracy of the
priate safety and health practices and determine the applica-
measurement technique is acceptable.
bility of regulatory limitations prior to use.
4.1.2 Example 2: Inconsistent metallographic preparation
2. Referenced Documents methods can cause the apparent amount of voids to vary
excessively indicating a poorly controlled thermal spray pro-
2.1 ASTM Standards:
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cess, while the use of consistent practice will regularly display
E 3 Guide for Preparation of Metallographic Specimens
2 the true microstructure and verify the consistency of the
E 7 Terminology Relating to Metallography
thermal spray process.
3. Terminology 4.2 During the development of TSC procedures, metallo-
graphic information is necessary to validate the efficacy of a
3.1 Definitions—For definitions of terms used in this guide,
specific application.
see Terminology E 7.
4.3 Cross sections are usually taken perpendicular to the
3.2 Definitions of Terms Specific to This Standard:
long axis of the specimen and prepared to reveal information
3.2.1 linear detachment, n—a region within aTSC in which
concerning the following:
two successively deposited splats of coating material have not
4.3.1 Variations in structure from surface to substrate,
metallurgically bonded.
4.3.2 The distribution of unmelted particles throughout the
3.2.2 splat, n—an individual globule of thermal sprayed
coating,
material that has been deposited on a substrate.
4.3.3 The distribution of linear detachment throughout the
3.2.3 taper mount, n—a metallographic specimen created
coating,
by mounting a feature, typically an interface or thin coating, at
4.3.4 The distribution of porosity throughout the coating,
4.3.5 The presence of contamination within the coating,
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4.3.6 The thickness of the coating (top coat and bond coat,
ThisguideisunderthejurisdictionofASTMCommitteeE04onMetallography
and is the direct responsibility of Subcommittee E04.01 on Sampling, Specimen
where applicable),
Preparation, and Photography.
4.3.7 The presence of interfacial contamination,
Current edition approved May 10, 2003. Published July 2003. Originally
4.3.8 The integrity of the interface between the coating and
approved in 1997. Last previous edition approved in 1997 as E 1920–97.
2
Annual Book of ASTM Standards, Vol. 03.01. substrate, and,
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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E1920–03
4.3.9 The integrity of the coating microstructure with re-
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