ASTM C664-10(2015)
(Test Method)Standard Test Methods for Thickness of Diffusion Coating
Standard Test Methods for Thickness of Diffusion Coating
SIGNIFICANCE AND USE
3.1 A diffusion coating is one produced by causing an element or elements to react with or diffuse into, or both, the surface of a metallic substrate, thus chemically altering the substrate adjacent to the surface. To appreciate the significance of coating thickness measurements one must understand the contributions to a particular coating of solid-solution zones in the substrate and reaction products such as intermetallic compounds.
SCOPE
1.1 These test methods cover two procedures for measuring the thickness of diffusion coatings.
1.2 Test Method A is the determination of the dimensional-change thickness, defined as the difference in the thickness of the part before and after coating. (The terms micrometer thickness and part growth are considered synonymous with dimensional change thickness.)
1.3 Test Method B is the determination of total coating thickness, defined as the distance between the observably unaffected substrate and the exterior surface of the coating. This includes the total of all included phases, zones and layers. (The term case depth is considered to be synonymous with total coating thickness.) The total coating thickness is determined by cross-sectioning the coating, preparing a metallurgical mount and microscopically measuring the coating thickness.
1.4 The total coating thickness as determined microscopically from a cross-section will usually be greater than, or equal to, the dimensional change thickness determined by part growth. When the coating is produced primarily by reaction with the substrate, the substrate-coating interface recedes as the substrate is consumed in the reaction. In such cases the difference between the total coating thickness and the dimensional change thickness is the thickness of the substrate consumed.
1.5 Diffusion coatings are usually formed at elevated temperatures for service at elevated temperatures. This means that diffusion coatings are dynamic systems which are continually undergoing changes while in an elevated-temperature environment. It is necessary to know that certain phases are growing at the expense of others and to know the previous history of a coating to understand the significance of coating thickness data.
1.6 Values in SI units are to be regarded as the standard. Inch-pound units are provided for information only.
1.7 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: C664 − 10 (Reapproved 2015)
Standard Test Methods for
Thickness of Diffusion Coating
This standard is issued under the fixed designation C664; 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.
INTRODUCTION
Diffusion coating is a thermally activated means of protecting certain iron, nickel, and cobalt based
alloys against severe operating conditions. It creates a chemically bonded, tenacious coating that acts
as a diffusion barrier against oxygen and other elements into the substrate to provide superior
oxidation, corrosion and erosion resistance up to 2100°F (1150°C). It is commonly used for gas
turbine components, power generation components, and diesel engines. This test procedure provides
a mean of determining the thickness of a diffusion coating.
1. Scope diffusion coatings are dynamic systems which are continually
undergoing changes while in an elevated-temperature environ-
1.1 These test methods cover two procedures for measuring
ment.Itisnecessarytoknowthatcertainphasesaregrowingat
the thickness of diffusion coatings.
the expense of others and to know the previous history of a
1.2 Test MethodAis the determination of the dimensional-
coating to understand the significance of coating thickness
change thickness, defined as the difference in the thickness of
data.
the part before and after coating. (The terms micrometer
1.6 Values in SI units are to be regarded as the standard.
thickness and part growth are considered synonymous with
Inch-pound units are provided for information only.
dimensional change thickness.)
1.7 This standard does not purport to address all of the
1.3 Test Method B is the determination of total coating
safety concerns, if any, associated with its use. It is the
thickness, defined as the distance between the observably
responsibility of the user of this standard to establish appro-
unaffected substrate and the exterior surface of the coating.
priate safety and health practices and determine the applica-
This includes the total of all included phases, zones and layers.
bility of regulatory limitations prior to use.
(Thetermcasedepthisconsideredtobesynonymouswithtotal
coatingthickness.)Thetotalcoatingthicknessisdeterminedby
2. Referenced Documents
cross-sectioning the coating, preparing a metallurgical mount
2.1 ASTM Standards:
and microscopically measuring the coating thickness.
D374Test Methods for Thickness of Solid Electrical Insu-
1.4 The total coating thickness as determined microscopi-
lation (Withdrawn 2013)
cally from a cross-section will usually be greater than, or equal
E3Guide for Preparation of Metallographic Specimens
to, the dimensional change thickness determined by part
3. Significance and Use
growth. When the coating is produced primarily by reaction
withthesubstrate,thesubstrate-coatinginterfacerecedesasthe 3.1 A diffusion coating is one produced by causing an
substrate is consumed in the reaction. In such cases the element or elements to react with or diffuse into, or both, the
difference between the total coating thickness and the dimen- surface of a metallic substrate, thus chemically altering the
sional change thickness is the thickness of the substrate
substrate adjacent to the surface.To appreciate the significance
consumed. of coating thickness measurements one must understand the
contributions to a particular coating of solid-solution zones in
1.5 Diffusion coatings are usually formed at elevated tem-
the substrate and reaction products such as intermetallic
peratures for service at elevated temperatures. This means that
compounds.
1 2
These test methods are under the jurisdiction of ASTM Committee B08 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Metallic and Inorganic Coatingsand are the direct responsibility of Subcommittee contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
B08.12 on Materials for Porcelain Enamel and Ceramic-Metal Systems. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved May 1, 2015. Published June 2015. Originally the ASTM website.
approvedin1970.Lastpreviouseditionapprovedin2010asC664–87(2010).DOI: The last approved version of this historical standard is referenced on
10.1520/C0664-10R15. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C664 − 10 (2015)
4. Test Method A time, if employed, will be by mutual agreement between the
customer and vendor. The etching procedure will clearly
4.1 Apparatus—The instrument shall be a machinist’s type
demark the boundaries of the coating as well as properly
micrometer without a locking device. If calibrated in inches, it
differentiate included zones, if it is desirable to measure their
shall be constructed with a vernier reading to 0.0001 in. (0.1
thickness as well.
mil). If calibrated in metric units, it shall be capable of reading
5.2.5 Measure the total coating thickness microscopically
to 0.01 mm. It shall have a ratchet or similar mechanism, such
with the aid of a calibrated-filar eyepiece, or by direct
as a friction thimble, for controlling measuring pressure and
measurement of a projected image on ground glass. Magnify
shallhaveanvilandspindlesurfaces6.00 60.03mm(0.250 6
the coating a minimum of 250× diameters, although 500× is
0.001 in.) in dia
...
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: C664 − 10 C664 − 10 (Reapproved 2015)
Standard Test Methods for
Thickness of Diffusion Coating
This standard is issued under the fixed designation C664; 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.
INTRODUCTION
Diffusion coating is a thermally activated means of protecting certain iron, nickel, and cobalt based
alloys against severe operating conditions. It creates a chemically bonded, tenacious coating that acts
as a diffusion barrier against oxygen and other elements into the substrate to provide superior
oxidation, corrosion and erosion resistance up to 2100°F (1150°C). It is commonly used for gas
turbine components, power generation components, and diesel engines. This test procedure provides
a mean of determining the thickness of a diffusion coating.
1. Scope
1.1 These test methods cover two procedures for measuring the thickness of diffusion coatings.
1.2 Test Method A is the determination of the dimensional-change thickness, defined as the difference in the thickness of the
part before and after coating. (The terms micrometer thickness and part growth are considered synonymous with dimensional
change thickness.)
1.3 Test Method B is the determination of total coating thickness, defined as the distance between the observably unaffected
substrate and the exterior surface of the coating. This includes the total of all included phases, zones and layers. (The term case
depth is considered to be synonymous with total coating thickness.) The total coating thickness is determined by cross-sectioning
the coating, preparing a metallurgical mount and microscopically measuring the coating thickness.
1.4 The total coating thickness as determined microscopically from a cross-section will usually be greater than, or equal to, the
dimensional change thickness determined by part growth. When the coating is produced primarily by reaction with the substrate,
the substrate-coating interface recedes as the substrate is consumed in the reaction. In such cases the difference between the total
coating thickness and the dimensional change thickness is the thickness of the substrate consumed.
1.5 Diffusion coatings are usually formed at elevated temperatures for service at elevated temperatures. This means that
diffusion coatings are dynamic systems which are continually undergoing changes while in an elevated-temperature environment.
It is necessary to know that certain phases are growing at the expense of others and to know the previous history of a coating to
understand the significance of coating thickness data.
1.6 Values in SI units are to be regarded as the standard. Inch-pound units are provided for information only.
1.7 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 and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D374 Test Methods for Thickness of Solid Electrical Insulation (Withdrawn 2013)
E3 Guide for Preparation of Metallographic Specimens
These test methods are under the jurisdiction of ASTM Committee B08 on Metallic and Inorganic Coatings and are the direct responsibility of Subcommittee B08.12
on Materials for Porcelain Enamel and Ceramic-Metal Systems.
Current edition approved April 1, 2010May 1, 2015. Published May 2010June 2015. Originally approved in 1970. Last previous edition approved in 20052010 as
C664 – 87(2005).(2010). DOI: 10.1520/C0664-10.10.1520/C0664-10R15.
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.
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
C664 − 10 (2015)
3. Significance and Use
3.1 A diffusion coating is one produced by causing an element or elements to react with or diffuse into, or both, the surface of
a metallic substrate, thus chemically altering the substrate adjacent to the surface. To appreciate the significance of coating
thickness measurements one must understand the contributions to a particular coating of solid-solution zones in the substrate and
reaction products such as intermetallic compounds.
4. Test Method A
4.1 Apparatus—The instrument shall be a machinist’s type micrometer without a locking device. If calibrated in inches, it shall
be constructed with a vernier reading to 0.0001 in. (0.1 mil). If calibrated in metric units, it shall be capable of reading to 0.01
mm. It shall have a ratchet or similar mechanism, such as a friction thimble, for controlling measuring pressure and shall have anvil
and spindle surfaces 6.00 6 0.03 mm (0.250 6 0.001 in.) in diameter. It shall meet all other requirements and calibration procedure
for Method A of Test Method D374.
4.2 Procedure:
4.2.1 Clean the area selected for coating-thickness measurement of dust or other powdery materials prior to coating. Record the
precise area to be measured, so that the same area can be remeasured after coating.
4.2.2 T
...
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