ASTM D7690-11
(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
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.
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.
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.
Ferrographic analysis, as described in this practice, provides additional particle identification capabilities beyond methods described in Guide 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 important distinctions bet...
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.
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Standards Content (Sample)
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Designation: D7690 − 11
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 3. Terminology
1.1 Thispracticecoverstheidentificationbyopticalmicros- 3.1 Definitions:
copy of wear and contaminant particles commonly found in
3.1.1 abrasion, n—wearbydisplacementofmaterialcaused
used lubricant and hydraulic oil samples that have been
by hard particles or hard protuberances. D4175
deposited on ferrograms. This practice relates to the identifi-
3.1.2 abrasive wear, n—wear due to hard particles or hard
cation of particles, but not to methods of determining particle
protuberancesforcedagainstandmovingalongasolidsurface.
concentration.
G40
1.2 This practice interfaces with but generally excludes
3.1.3 adhesive wear, n—wear due to localized bonding
particles generated in the absence of lubrication, such as may
between contacting solid surfaces leading to material transfer
be generated by erosion, impaction, gouging, or polishing.
between the two surfaces or loss from either surface. G40
1.3 The values stated in SI units are to be regarded as
3.1.4 break-in, n—See run-in. D4175, G40
standard. No other units of measurement are included in this
3.1.5 break in, v—See run in. G40
standard.
1.4 This standard does not purport to address all of the 3.1.6 catastrophic wear, n—rapidly occurring or accelerat-
ing surface damage, deterioration, or change of shape caused
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- by wear to such a degree that the service life of a part is
appreciably shortened or its function is destroyed. G40
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
3.1.7 corrosion, n—chemical or electrochemical reaction
between a material, usually a metal surface, and its environ-
2. Referenced Documents
ment that can produce a deterioration of the material and its
2.1 ASTM Standards:
properties. D4175
D4057Practice for Manual Sampling of Petroleum and
3.1.8 corrosive wear, n—wear in which chemical or electro-
Petroleum Products
chemical reaction with the environment is significant. G40
D4175 Terminology Relating to Petroleum, Petroleum
Products, and Lubricants
3.1.9 debris, n—in tribology, particles that have become
D7684Guide for Microscopic Characterization of Particles
detached in a wear or erosion process. G40
from In-Service Lubricants
3.1.10 debris, n—in internal combustion engines,solid con-
G40Terminology Relating to Wear and Erosion
taminant 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
This practice is under the jurisdiction ofASTM Committee D02 on Petroleum
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-
contact.
mittee D02.96.06 on Practices and Techniques for Prediction and Determination of
3.1.12.1 Discussion—Here the term fretting refers only to
Microscopic Wear and Wear-related Properties.
the nature of the motion without reference to the wear,
Current edition approved Jan. 1, 2011. Published March 2011. DOI: 10.1520/
D7690–11.
corrosion,orotherdamagethatmayensue.Theterm frettingis
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
often used to denote fretting corrosion and other forms of
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
fretting wear. Usage in this sense is discouraged due to the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. ambiguity that may arise. G40
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7690 − 11
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
3.1.29 triboelement, n—oneoftwoormoresolidbodiesthat
3.1.14 friction, n—resistance to sliding exhibited by two
comprise a sliding, rolling, or abrasive contact, or a body
surfaces in contact with each other. Basically there are two
subjected to impingement or cavitation. (Each triboelement
frictional properties exhibited by any surface; static friction
contains one or more tribosurfaces.)
and kinetic friction. D4175
3.1.29.1 Discussion—Contacting triboelements may be in
3.1.15 impact wear, n—wear due to collisions between two
direct contact or may be separated by an intervening lubricant,
solid bodies where some component of the motion is perpen-
oxide, or other film that affects tribological interactions be-
dicular to the tangential plane of contact. G40
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
second (mPa.s) and is often used. D4175
3.1.19 rolling, v—in tribology,motioninadirectionparallel
3.1.32 wear, n—damagetoasolidsurface,usuallyinvolving
to the plane of a revolute body (ball, cylinder, wheel, and so
progressive loss or displacement of material, due to relative
forth)onasurfacewithoutrelativeslipbetweenthesurfacesin
motion between that surface and a contacting substance or
all or part of the contact area. G40
substances. G40, D4175
3.1.20 rolling contact fatigue, n—damage process in a
3.2 Definitions of Terms Specific to This Standard:
triboelement subjected to repeated rolling contact loads, in-
3.2.1 abrasive wear particles, n—long wire-like particles in
volving the initiation and propagation of fatigue cracks in or
the form of loops or spirals generated due to hard, abrasive
under the contact surface, eventually culminating in surface
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
3.2.2 analytical ferrography, n—technique whereby par-
both, which are uncharacteristic of the given tribological
ticles from an oil sample deposited by a ferrograph are
system’s long term behavior. (Synonym: break-in, wear-in.)
identifiedtoaidinestablishingwearmodeinsideanoil-wetted
D4175, G40
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
anextraneoussourceintothelubricantofamachineorengine.
3.1.26 soot, n—in internal combustion,engines,sub-micron
3.2.6 chunks, n—free metal particles >5 µm with a shape
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
3.1.27 spalling, n—in tribology, the separation of macro- oxidized particles caused by corrosive attack.
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.
3.1.28 three-body abrasive wear, n—form of abrasive wear 3.2.9 entry, n—entryareaoftheferrogram,regionwherethe
in which wear is produced by loose particles introduced or sample first touches down onto the glass surface of the
generated between the contacting surfaces. ferrogramandwherethelargestferrousparticlesaredeposited.
D7690 − 11
3.2.10 ferrograph, n—apparatus to magnetically separate 3.2.25 severe wear particles, n—free metal particles >15
and deposit wear and contaminant particles onto a specially µm, and with major dimension-to-thickness ratios between 5:1
prepared glass microscope slide. and 30:1.
3.2.11 ferrogram, n—specially prepared glass microscope 3.2.26 spheres, n—metal spheres may be the result of
slide that has ferrographically deposited particles on its sur- incipient rolling contact fatigue or they may be contaminant
face. particles from welding, grinding, coal burning and steel manu-
facturing. Spheres may also be caused by electro-pitting.
3.2.12 fibers, n—long, thin, nonmetallic particles.
3.2.27 wear particles, n—particles generated from a wear-
3.2.13 friction polymers, n—these are characterized by
ing surface of a machine.
small metal particles embedded in an amorphous matrix.
3.2.14 nonferrous metal particles, n—free metal particles
4. Summary of Practice
composed of any metal except iron. All common nonferrous
4.1 Periodic in-service lubricant samples are collected from
metals behave nonmagnetically except nickel.
a machine or engine as part of a routine condition monitoring
3.2.15 nonmetallic particles, n—particles comprised of
program.Aferrogram is prepared from the sample to separate
compounds, organic material, glasses, etc., that have bound
particles from sample fluid. The ferrogram is subsequently
electrons in their atomic structure.
examined using an optical microscope to identify the types of
3.2.16 nonmetallic amorphous particles, n—particles with-
particles present to aid in identifying the wear mode occurring
outlongrangeatomicorderthataretransparentandthatdonot
in the oil-wetted path of the machine.
appear bright in polarized light.
4.2 In usual practice of a routine condition monitoring
3.2.17 nonmetallic crystalline particles, n—particles with
program, a ferrogram is not prepared for every sample taken,
long range atomic structure that appear bright in polarized
but may be prepared when routine tests such as spectrochemi-
light. These may be single crystals but are most likely
cal analysis, particle counting or ferrous debris monitoring
polycrystalline or polycrystalline agglomerates.
indicate abnormal results.
3.2.18 platelets, n—flat, free metal wear particles that are
4.3 Theuserofthispracticeemploysconsistentterminology
longer and wider than they are thick. They have a major
to achieve accepted and understandable interpretations when
dimension-to-thickness ratio in the range of approximately 5:1
communicatinginstructionsandfindingsbasedonferrographic
to 10:1 or more.
analysis.
3.2.19 red oxide particles, n—rust particles present as poly-
5. Significance and Use
crystalline agglomerates of Fe O appearing orange in re-
2 3
flected white light. These are usually due to water in the
5.1 The objective of ferrography is to diagnose the opera-
lubricating system.
tional condition of the machine sampled based on the quantity
3.2.20 red oxide sliding particles, n—sliding wear particles
and type of particles observed in the oil. After break-in,
that appear gray in reflected white light, but are dull reddish- normally running machines exhibit consistent particle concen-
brown in white transmitted light.
tration and particle types from sample to sample. An increase
in particle concentration, accompanied by an increase in size
3.2.21 reworked particles, n—large, very thin, free metal
and severity of particle types is indicative of initiation of a
particles often in the range of 20 to 50 µm in major dimension
fault. This practice describes commonly found particles in
with the frequent occurrence of holes consistent with the
in-service lubricants, but does not address methodology for
explanation these are formed by the passage of a wear particle
quantification of particle concentration.
through a rolling contact.
5.2 This practice is provided to promote improved and
3.2.22 rolling contact fatigue particles, n—flat platelets,
expandeduseofferrographicanalysiswithin-servicelubricant
withtheirlengthmoreorlessequaltotheirwidth,withsmooth
analysis. It helps overcome some perceived complexity and
surfaces, random, jagged and irregularly shaped circumfer-
resultingintimidationthateffectivelylimitsferrographicanaly-
ences and a major dimension-to-thickness ratio in the range of
sis to the hands of a specialized and very limited number of
approximately 5:1 to 10:1 or more.
practitioners.Standardizedterminologyandcommonreporting
3.2.23 rubbing wear particles, n—particles generated as a
formats provide consistent interpretation and general under-
result of sliding wear in a machine, sometimes called mild
standing
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