ASTM D7690-11(2017)
(Practice)Standard Practice for Microscopic Characterization of Particles from In-Service Lubricants by Analytical Ferrography
Standard Practice for Microscopic Characterization of Particles from In-Service Lubricants by Analytical Ferrography
SIGNIFICANCE AND USE
5.1 The objective of ferrography is to diagnose the operational condition of the machine sampled based on the quantity and type of particles observed in the oil. After break-in, normally running machines exhibit consistent particle concentration and particle types from sample to sample. An increase in particle concentration, accompanied by an increase in size and severity of particle types is indicative of initiation of a fault. This practice describes commonly found particles in in-service lubricants, but does not address methodology for quantification of particle concentration.
5.2 This practice is provided to promote improved and expanded use of ferrographic analysis with in-service lubricant analysis. It helps overcome some perceived complexity and resulting intimidation that effectively limits ferrographic analysis to the hands of a specialized and very limited number of practitioners. Standardized terminology and common reporting formats provide consistent interpretation and general understanding.
5.3 Without particulate debris analysis, in-service lubricant analysis results often fall short of concluding likely root cause or potential severity from analytical results because of missing information about the possible identification or extent of damaging mechanisms.
5.4 Ferrographic analysis, as described in this practice, provides additional particle identification capabilities beyond methods described in Guide D7684 for the following reasons:
(1) The ferrographic particle separation method is magnetic thus making it possible to readily distinguish between ferrous and nonferrous wear particles.
(2) Ferrography separates ferrous (magnetic) particles by size.
(3) Deposition is on a glass substrate so that particles may be examined using transmitted light as well as reflected light allowing particle types to be identified that cannot be identified when examination is done using only reflected light.
(4) Ferrograms may be heat treated providing im...
SCOPE
1.1 This practice covers the identification by optical microscopy of wear and contaminant particles commonly found in used lubricant and hydraulic oil samples that have been deposited on ferrograms. This practice relates to the identification of particles, but not to methods of determining particle concentration.
1.2 This practice interfaces with but generally excludes particles generated in the absence of lubrication, such as may be generated by erosion, impaction, gouging, or polishing.
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 and health 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.
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Designation: D7690 − 11 (Reapproved 2017)
Standard Practice for
Microscopic Characterization of Particles from In-Service
Lubricants by Analytical Ferrography
This standard is issued under the fixed designation D7690; 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.
1. Scope D7684Guide for Microscopic Characterization of Particles
from In-Service Lubricants
1.1 Thispracticecoverstheidentificationbyopticalmicros-
G40Terminology Relating to Wear and Erosion
copy of wear and contaminant particles commonly found in
used lubricant and hydraulic oil samples that have been
3. Terminology
deposited on ferrograms. This practice relates to the identifi-
3.1 Definitions:
cation of particles, but not to methods of determining particle
3.1.1 abrasion, n—wearbydisplacementofmaterialcaused
concentration.
by hard particles or hard protuberances. D4175
1.2 This practice interfaces with but generally excludes
3.1.2 abrasive wear, n—wear due to hard particles or hard
particles generated in the absence of lubrication, such as may
protuberancesforcedagainstandmovingalongasolidsurface.
be generated by erosion, impaction, gouging, or polishing.
G40
1.3 The values stated in SI units are to be regarded as
3.1.3 adhesive wear, n—wear due to localized bonding
standard. No other units of measurement are included in this
between contacting solid surfaces leading to material transfer
standard.
between the two surfaces or loss from either surface. G40
1.4 This standard does not purport to address all of the
3.1.4 break-in, n—See run-in. D4175, G40
safety concerns, if any, associated with its use. It is the
3.1.5 break in, v—See run in. G40
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- 3.1.6 catastrophic wear, n—rapidly occurring or accelerat-
bility of regulatory limitations prior to use.
ing surface damage, deterioration, or change of shape caused
1.5 This international standard was developed in accor- by wear to such a degree that the service life of a part is
dance with internationally recognized principles on standard-
appreciably shortened or its function is destroyed. G40
ization established in the Decision on Principles for the
3.1.7 corrosion, n—chemical or electrochemical reaction
Development of International Standards, Guides and Recom-
between a material, usually a metal surface, and its environ-
mendations issued by the World Trade Organization Technical
ment that can produce a deterioration of the material and its
Barriers to Trade (TBT) Committee.
properties. D4175
3.1.8 corrosive wear, n—wear in which chemical or electro-
2. Referenced Documents
chemical reaction with the environment is significant. G40
2.1 ASTM Standards:
3.1.9 debris, n—in tribology, particles that have become
D4057Practice for Manual Sampling of Petroleum and
detached in a wear or erosion process. G40
Petroleum Products
D4175Terminology Relating to Petroleum Products, Liquid 3.1.10 debris, n—in internal combustion engines,solid con-
taminant materials unintentionally introduced in to the engine
Fuels, and Lubricants
or resulting from wear. D4175
3.1.11 fatigue wear, n—wear of a solid surface caused by
This practice is under the jurisdiction ofASTM Committee D02 on Petroleum
fracture arising from material fatigue. G40
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-
mittee D02.96.06 on Practices and Techniques for Prediction and Determination of
3.1.12 fretting, n—in tribology, small amplitude oscillatory
Microscopic Wear and Wear-related Properties.
motion, usually tangential, between two solid surfaces in
CurrenteditionapprovedMay1,2017.PublishedJuly2017.Originallyapproved
contact.
in 2011. Last previous edition approved in 2011 as D7690–11. DOI: 10.1520/
D7690-11R17.
3.1.12.1 Discussion—Here the term fretting refers only to
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
the nature of the motion without reference to the wear,
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
corrosion,orotherdamagethatmayensue.Theterm frettingis
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. often used to denote fretting corrosion and other forms of
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7690 − 11 (2017)
fretting wear. Usage in this sense is discouraged due to the 3.1.28 three-body abrasive wear, n—form of abrasive wear
ambiguity that may arise. G40 in which wear is produced by loose particles introduced or
generated between the contacting surfaces.
3.1.13 fretting wear, n—wear arising as a result of fretting.
3.1.28.1 Discussion—In tribology, loose particles are con-
(See fretting.) G40
sidered to be a “third body.” G40
3.1.14 friction, n—resistance to sliding exhibited by two
3.1.29 triboelement, n—oneoftwoormoresolidbodiesthat
surfaces in contact with each other. Basically there are two
comprise a sliding, rolling, or abrasive contact, or a body
frictional properties exhibited by any surface; static friction
subjected to impingement or cavitation. (Each triboelement
and kinetic friction. D4175
contains one or more tribosurfaces.)
3.1.15 impact wear, n—wear due to collisions between two
3.1.29.1 Discussion—Contacting triboelements may be in
solid bodies where some component of the motion is perpen-
direct contact or may be separated by an intervening lubricant,
dicular to the tangential plane of contact. G40
oxide, or other film that affects tribological interactions be-
tween them. G40
3.1.16 lubricant, n—any material interposed between two
3.1.30 two-body abrasive wear, n—formofabrasivewearin
surfacesthatreducesthefrictionorwearbetweenthem. D4175
which the hard particles or protuberances which produce the
3.1.17 lubricating oil, n—liquid lubricant, usually compris-
wearofonebodyarefixedonthesurfaceoftheopposingbody.
ing several ingredients, including a major portion of base oil
G40
and minor portions of various additives. D4175
3.1.31 viscosity, n—ratio between the applied shear stress
3.1.18 pitting, n—in tribology, form of wear characterized
and rate of shear. It is sometimes called the coefficient of
by the presence of surface cavities the formation of which is
dynamic viscosity. This value is thus a measure of the
attributed to processes such as fatigue, local adhesion, or
resistance to flow of the liquid. The SI unit of viscosity is the
cavitation. G40
pascal second (Pa.s). The centipoise (cP) is one millipascal
3.1.19 rolling, v—in tribology,motioninadirectionparallel second (mPa.s) and is often used. D4175
to the plane of a revolute body (ball, cylinder, wheel, and so
3.1.32 wear, n—damagetoasolidsurface,usuallyinvolving
forth)onasurfacewithoutrelativeslipbetweenthesurfacesin
progressive loss or displacement of material, due to relative
all or part of the contact area. G40
motion between that surface and a contacting substance or
substances. G40, D4175
3.1.20 rolling contact fatigue, n—damage process in a
triboelement subjected to repeated rolling contact loads, in-
3.2 Definitions of Terms Specific to This Standard:
volving the initiation and propagation of fatigue cracks in or
3.2.1 abrasive wear particles, n—long wire-like particles in
under the contact surface, eventually culminating in surface
the form of loops or spirals generated due to hard, abrasive
pits or spalls. G40
particles present between wearing surfaces of unequal hard-
ness.
3.1.21 run-in, n—in tribology, initial transition process
3.2.1.1 Discussion—Sometimes called cutting wear par-
occurring in newly established wearing contacts, often accom-
ticles.
panied by transients in coefficient of friction, or wear rate, or
both, which are uncharacteristic of the given tribological 3.2.2 analytical ferrography, n—technique whereby par-
system’s long term behavior. (Synonym: break-in, wear-in.) ticles from an oil sample deposited by a ferrograph are
D4175, G40 identified to aid in establishing wear mode inside an oil-wetted
path of a machine.
3.1.22 run in, v—in tribology, to apply a specified set of
3.2.3 bichromatic microscope, n—optical microscope
initial operating conditions to a tribological system to improve
equipped with illumination sources both above and below the
its long term frictional or wear behavior, or both. (Synonym:
microscope stage such that objects may be viewed either with
break in,v,and wear in, v.) See also run-in,n) G40
reflected light, or with transmitted light, or with both simulta-
3.1.23 rust, n—of ferrous alloys, a corrosion product con-
neously.
sisting primarily of hydrated iron oxides. D4175
3.2.4 black oxides of iron, n—generallysmall,blackclusters
3.1.24 scoring, n—in tribology, severe form of wear char-
with pebbled surfaces showing small dots of blue and orange
acterized by the formation of extensive grooves and scratches
color. These are nonstoichiometric compounds containing a
in the direction of sliding. D4175, G40
mixture of Fe O,Fe O and FeO.
3 4 2 3
3.1.25 sliding wear, n—wear due to the relative motion in
3.2.5 contaminant particles, n—particles introduced from
the tangential plane of contact between two solid bodies. G40
an extraneous source into the lubricant of a machine or engine.
3.2.6 chunks, n—free metal particles >5µm with a shape
3.1.26 soot, n—in internal combustion,engines,sub-micron
size particles, primarily carbon, created in the combustion factor (major dimension to thickness ratio) of <5:1.
chamber as products of incomplete combustion. D4175
3.2.7 corrosive wear debris, n—extremely fine partially
oxidized particles caused by corrosive attack.
3.1.27 spalling, n—in tribology, the separation of macro-
scopic particles from a surface in the form of flakes or chips, 3.2.8 dark metallo-oxide particles, n—partially oxidized
usuallyassociatedwithrollingelementbearingsandgearteeth, ferrous wear particles indicating high heat during generation
but also resulting from impact events. G40 most likely due to lubricant starvation.
D7690 − 11 (2017)
3.2.9 entry, n—entryareaoftheferrogram,regionwherethe 3.2.24 severe sliding wear particles, n—severe wear par-
sample first touches down onto the glass surface of the ticles displaying surface striations and straight edges.
ferrogramandwherethelargestferrousparticlesaredeposited.
3.2.25 severe wear particles, n—free metal particles
>15µm,andwithmajordimension-to-thicknessratiosbetween
3.2.10 ferrograph, n—apparatus to magnetically separate
and deposit wear and contaminant particles onto a specially 5:1 and 30:1.
prepared glass microscope slide.
3.2.26 spheres, n—metal spheres may be the result of
3.2.11 ferrogram, n—specially prepared glass microscope incipient rolling contact fatigue or they may be contaminant
particles from welding, grinding, coal burning and steel manu-
slide that has ferrographically deposited particles on its sur-
face. facturing. Spheres may also be caused by electro-pitting.
3.2.27 wear particles, n—particles generated from a wear-
3.2.12 fibers, n—long, thin, nonmetallic particles.
ing surface of a machine.
3.2.13 friction polymers, n—these are characterized by
small metal particles embedded in an amorphous matrix.
4. Summary of Practice
3.2.14 nonferrous metal particles, n—free metal particles
4.1 Periodic in-service lubricant samples are collected from
composed of any metal except iron. All common nonferrous
a machine or engine as part of a routine condition monitoring
metals behave nonmagnetically except nickel.
program.Aferrogram is prepared from the sample to separate
particles from sample fluid. The ferrogram is subsequently
3.2.15 nonmetallic particles, n—particles comprised of
examined using an optical microscope to identify the types of
compounds, organic material, glasses, etc., that have bound
particles present to aid in identifying the wear mode occurring
electrons in their atomic structure.
in the oil-wetted path of the machine.
3.2.16 nonmetallic amorphous particles, n—particles with-
4.2 In usual practice of a routine condition monitoring
outlongrangeatomicorderthataretransparentandthatdonot
program, a ferrogram is not prepared for every sample taken,
appear bright in polarized light.
but may be prepared when routine tests such as spectrochemi-
3.2.17 nonmetallic crystalline particles, n—particles with
cal analysis, particle counting or ferrous debris monitoring
long range atomic structure that appear bright in polarized
indicate abnormal results.
light. These may be single crystals but are most likely
4.3 Theuserofthispracticeemploysconsistentterminology
polycrystalline or polycrystalline agglomerates.
to achieve accepted and understandable interpretations when
3.2.18 platelets, n—flat, free metal wear particles that are
communicatinginstructionsandfindingsbasedonferrographic
longer and wider than they are thick. They have a major
analysis.
dimension-to-thickness ratio in the range of approximately 5:1
to 10:1 or more.
5. Significance and Use
3.2.19 red oxide particles, n—rust particles present as poly-
5.1 The objective of ferrography is to diagnose the opera-
crystalline agglomerates of Fe O appearing orange in re-
2 3
tional condition of the machine sampled based on the quantity
flected white light. These are usually due to water in the
and type of particles observed in the oil. After break-in,
lubricating system.
normally running machines exhibit consistent particle concen-
tration and particle types from sample to sample. An increase
3.2.20 red oxide sliding particles, n—sliding wear particles
in particle concentration, accompanied by an increase in size
that appear gray in reflected white light, but are dull reddish-
brown in white transmitted light. and severity of particle types is indicative of initiation of a
fault. This practice describes commonly found particles in
3.2.21 reworked particles, n—large, very thin, free metal
in-service lubricants, but does not address methodology for
particles often in the range of 20µm to 50µm in major
quantification of particle concentration.
dimension with the frequent occurrence of holes consistent
5.2 This practice is provided to promote improved and
withtheexplanationtheseareformedbythepassageofawear
particle through a rolling contact. expandeduseofferrographicanalysiswithin-servicelubricant
analysis. It helps overcome some perceived complexity and
3.2.22 rolling contact fatigue particles, n—flat platelets,
resultingintimidationthat
...
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: D7690 − 11 D7690 − 11 (Reapproved 2017)
Standard Practice for
Microscopic Characterization of Particles from In-Service
Lubricants by Analytical Ferrography
This standard is issued under the fixed designation D7690; 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 practice covers the identification by optical microscopy of wear and contaminant particles commonly found in used
lubricant and hydraulic oil samples that have been deposited on ferrograms. This practice relates to the identification of particles,
but not to methods of determining particle concentration.
1.2 This practice interfaces with but generally excludes particles generated in the absence of lubrication, such as may be
generated by erosion, impaction, gouging, or polishing.
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 and health 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.
2. Referenced Documents
2.1 ASTM Standards:
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D7684 Guide for Microscopic Characterization of Particles from In-Service Lubricants
G40 Terminology Relating to Wear and Erosion
This practice is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.96.06 on Practices and Techniques for Prediction and Determination of Microscopic Wear and Wear-related Properties.
Current edition approved Jan. 1, 2011May 1, 2017. Published March 2011July 2017. Originally approved in 2011. Last previous edition approved in 2011 as D7690 – 11.
DOI: 10.1520/D7690–11.10.1520/D7690-11R17.
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7690 − 11 (2017)
3. Terminology
3.1 Definitions:
3.1.1 abrasion, n—wear by displacement of material caused by hard particles or hard protuberances. D4175
3.1.2 abrasive wear, n—wear due to hard particles or hard protuberances forced against and moving along a solid surface. G40
3.1.3 adhesive wear, n—wear due to localized bonding between contacting solid surfaces leading to material transfer between
the two surfaces or loss from either surface. G40
3.1.4 break-in, n—See run-in. D4175, G40
3.1.5 break in, v—See run in. G40
3.1.6 catastrophic wear, n—rapidly occurring or accelerating surface damage, deterioration, or change of shape caused by wear
to such a degree that the service life of a part is appreciably shortened or its function is destroyed. G40
3.1.7 corrosion, n—chemical or electrochemical reaction between a material, usually a metal surface, and its environment that
can produce a deterioration of the material and its properties. D4175
3.1.8 corrosive wear, n—wear in which chemical or electrochemical reaction with the environment is significant. G40
3.1.9 debris, n—in tribology, particles that have become detached in a wear or erosion process. G40
3.1.10 debris, n—in internal combustion engines,solid contaminant materials unintentionally introduced in to the engine or
resulting from wear. D4175
3.1.11 fatigue wear, n—wear of a solid surface caused by fracture arising from material fatigue. G40
3.1.12 fretting, n—in tribology, small amplitude oscillatory motion, usually tangential, between two solid surfaces in contact.
3.1.12.1 Discussion—
Here the term fretting refers only to the nature of the motion without reference to the wear, corrosion, or other damage that may
ensue. The term fretting is often used to denote fretting corrosion and other forms of fretting wear. Usage in this sense is
discouraged due to the ambiguity that may arise. G40
3.1.13 fretting wear, n—wear arising as a result of fretting. (See fretting.) G40
3.1.14 friction, n—resistance to sliding exhibited by two surfaces in contact with each other. Basically there are two frictional
properties exhibited by any surface; static friction and kinetic friction. D4175
3.1.15 impact wear, n—wear due to collisions between two solid bodies where some component of the motion is perpendicular
to the tangential plane of contact. G40
3.1.16 lubricant, n—any material interposed between two surfaces that reduces the friction or wear between them. D4175
3.1.17 lubricating oil, n—liquid lubricant, usually comprising several ingredients, including a major portion of base oil and
minor portions of various additives. D4175
3.1.18 pitting, n—in tribology, form of wear characterized by the presence of surface cavities the formation of which is
attributed to processes such as fatigue, local adhesion, or cavitation. G40
3.1.19 rolling, v—in tribology, motion in a direction parallel to the plane of a revolute body (ball, cylinder, wheel, and so forth)
on a surface without relative slip between the surfaces in all or part of the contact area. G40
3.1.20 rolling contact fatigue, n—damage process in a triboelement subjected to repeated rolling contact loads, involving the
initiation and propagation of fatigue cracks in or under the contact surface, eventually culminating in surface pits or spalls. G40
3.1.21 run-in, n—in tribology, initial transition process occurring in newly established wearing contacts, often accompanied by
transients in coefficient of friction, or wear rate, or both, which are uncharacteristic of the given tribological system’s long term
behavior. (Synonym: break-in,wear-in.) D4175, G40
3.1.22 run in, v—in tribology, to apply a specified set of initial operating conditions to a tribological system to improve its long
term frictional or wear behavior, or both. (Synonym: break in, v, and wear in, v.) See also run-in, n) G40
3.1.23 rust, n—of ferrous alloys, a corrosion product consisting primarily of hydrated iron oxides. D4175
3.1.24 scoring, n—in tribology, severe form of wear characterized by the formation of extensive grooves and scratches in the
direction of sliding. D4175, G40
3.1.25 sliding wear, n—wear due to the relative motion in the tangential plane of contact between two solid bodies. G40
3.1.26 soot, n—in internal combustion, engines, sub-micron size particles, primarily carbon, created in the combustion chamber
as products of incomplete combustion. D4175
3.1.27 spalling, n—in tribology, the separation of macroscopic particles from a surface in the form of flakes or chips, usually
associated with rolling element bearings and gear teeth, but also resulting from impact events. G40
D7690 − 11 (2017)
3.1.28 three-body abrasive wear, n—form of abrasive wear in which wear is produced by loose particles introduced or generated
between the contacting surfaces.
3.1.28.1 Discussion—
In tribology, loose particles are considered to be a “third body.” G40
3.1.29 triboelement, n—one of two or more solid bodies that comprise a sliding, rolling, or abrasive contact, or a body subjected
to impingement or cavitation. (Each triboelement contains one or more tribosurfaces.)
3.1.29.1 Discussion—
Contacting triboelements may be in direct contact or may be separated by an intervening lubricant, oxide, or other film that affects
tribological interactions between them. G40
3.1.30 two-body abrasive wear, n—form of abrasive wear in which the hard particles or protuberances which produce the wear
of one body are fixed on the surface of the opposing body. G40
3.1.31 viscosity, n—ratio between the applied shear stress and rate of shear. It is sometimes called the coefficient of dynamic
viscosity. This value is thus a measure of the resistance to flow of the liquid. The SI unit of viscosity is the pascal second (Pa.s).
The centipoise (cP) is one millipascal second (mPa.s) and is often used. D4175
3.1.32 wear, n—damage to a solid surface, usually involving progressive loss or displacement of material, due to relative motion
between that surface and a contacting substance or substances. G40, D4175
3.2 Definitions of Terms Specific to This Standard:
3.2.1 abrasive wear particles, n—long wire-like particles in the form of loops or spirals generated due to hard, abrasive particles
present between wearing surfaces of unequal hardness.
3.2.1.1 Discussion—
Sometimes called cutting wear particles.
3.2.2 analytical ferrography, n—technique whereby particles from an oil sample deposited by a ferrograph are identified to aid
in establishing wear mode inside an oil-wetted path of a machine.
3.2.3 bichromatic microscope, n—optical microscope equipped with illumination sources both above and below the microscope
stage such that objects may be viewed either with reflected light, or with transmitted light, or with both simultaneously.
3.2.4 black oxides of iron, n—generally small, black clusters with pebbled surfaces showing small dots of blue and orange color.
These are nonstoichiometric compounds containing a mixture of Fe O , Fe O and FeO.
3 4 2 3
3.2.5 contaminant particles, n—particles introduced from an extraneous source into the lubricant of a machine or engine.
3.2.6 chunks, n—free metal particles >5 μm >5 μm with a shape factor (major dimension to thickness ratio) of <5:1.
3.2.7 corrosive wear debris, n—extremely fine partially oxidized particles caused by corrosive attack.
3.2.8 dark metallo-oxide particles, n—partially oxidized ferrous wear particles indicating high heat during generation most
likely due to lubricant starvation.
3.2.9 entry, n—entry area of the ferrogram, region where the sample first touches down onto the glass surface of the ferrogram
and where the largest ferrous particles are deposited.
3.2.10 ferrograph, n—apparatus to magnetically separate and deposit wear and contaminant particles onto a specially prepared
glass microscope slide.
3.2.11 ferrogram, n—specially prepared glass microscope slide that has ferrographically deposited particles on its surface.
3.2.12 fibers, n—long, thin, nonmetallic particles.
3.2.13 friction polymers, n—these are characterized by small metal particles embedded in an amorphous matrix.
3.2.14 nonferrous metal particles, n—free metal particles composed of any metal except iron. All common nonferrous metals
behave nonmagnetically except nickel.
3.2.15 nonmetallic particles, n—particles comprised of compounds, organic material, glasses, etc., that have bound electrons in
their atomic structure.
3.2.16 nonmetallic amorphous particles, n—particles without long range atomic order that are transparent and that do not appear
bright in polarized light.
D7690 − 11 (2017)
3.2.17 nonmetallic crystalline particles, n—particles with long range atomic structure that appear bright in polarized light.
These may be single crystals but are most likely polycrystalline or polycrystalline agglomerates.
3.2.18 platelets, n—flat, free metal wear particles that are longer and wider than they are thick. They have a major
dimension-to-thickness ratio in the range of approximately 5:1 to 10:1 or more.
3.2.19 red oxide particles, n—rust particles present as polycrystalline agglomerates of Fe O appearing orange in reflected white
2 3
light. These are usually due to water in the lubricating system.
3.2.20 red oxide sliding particles, n—sliding wear particles that appear gray in reflected white light, but are dull reddish-brown
in white transmitted light.
3.2.21 reworked particles, n—large, very thin, free metal particles often in the range of 2020 μm to 50 μm 50 μm in major
dimension with the frequent occurrence of holes consistent with the explanation these are formed by the passage of a wear particle
through a rolling contact.
3.2.22 rolling contact fatigue particles, n—flat platelets, with their length more or less equal to their width, with smooth
surfaces, random, jagged and irregularly shaped circumferences and a major dimension-to-thickness ratio in the range of
approximately 5:1 to 10:1 or more.
3.2.23 rubbing wear particles, n—particles generated as a result of sliding wear in a machine, sometimes called mild adhesive
wear. Rubbing wear particles are free metal platelets with smooth surfaces, from approximately 0.50.5 μm to 15 μm 15 μm in major
dimension and with major dimension-to-thickness ratios from about 10:1 for larger particles and to about 3:1 for smaller particles.
Any free metal particle <5 μm <5 μm is classified as a rubbing wear particle regardless of shape factor unless it is a sphere.
3.2.24 severe sliding wear particles, n—severe wear particles displaying surface striations and straight edges.
3.2.25 severe wear particles, n—free metal particles >15 μm, >15 μm, and with major dimension-to-thickness ratios between
5:1 and 30:1.
3.2.26 spheres, n—metal spheres may be the result of incipient rolling contact fatigue or they may be contaminant particles from
welding, grinding, coal burning and steel manufacturing. Spheres may also be caused by electro-pitting.
3.2.27 wear particles, n—particles generated from a wearing surface of a machine.
4. Summary of Practice
4.1 Periodic in-service lubricant samples are collected from a machine or engine as part of a routine condition monitoring
program. A ferrogram is prepared from the sample to separate particles from sample fluid. The ferrogram is subsequently examined
using an optical microscope to identify the types of particles present to aid in identifying the wear mode occurring in the oil-wetted
path o
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