ASTM D7690-11(2021)
(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, health, and environmental 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.
General Information
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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: D7690 − 11 (Reapproved 2021)
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, health, and environmental practices and deter- 3.1.6 catastrophic wear, n—rapidly occurring or accelerat-
mine the applicability 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
contaminant materials unintentionally introduced in to the
Fuels, and Lubricants
engine 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
Current edition approved Oct. 1, 2021. Published November 2021. Originally
contact.
approved in 2011. Last previous edition approved in 2017 as D7690–11 (2017).
DOI: 10.1520/D7690-11R21.
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 (2021)
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 (2021)
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
with the explanation these are formed by the passage of a wear
particle through a rolling co
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