ASTM G73-98
(Practice)Standard Practice for Liquid Impingement Erosion Testing
Standard Practice for Liquid Impingement Erosion Testing
SCOPE
1.1 This practice concerns tests in which solid specimens are eroded or otherwise damaged by repeated discrete impacts of liquid drops or jets. Among the collateral forms of damage considered are degradation of optical properties of window materials, and penetration, separation, or destruction of coatings. The objective of the tests may be to determine the resistance to erosion or other damage of the materials or coatings under test, or to investigate the damage mechanisms and the effect of test variables. Because of the specialized nature of these tests and the desire in many cases to simulate to some degree the expected service environment, the promulgation of a method is not deemed practicable. This practice gives guidance in setting up a test, and specifies test and analysis procedures and reporting requirements that can be followed even with quite widely differing materials, test facilities, and test conditions. It also provides a standardized scale of erosion resistance numbers applicable to metals and other structural materials.
1.2 This standard does not purport to address all of the safety problems, 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:G73–98
Standard Practice for
Liquid Impingement Erosion Testing
ThisstandardisissuedunderthefixeddesignationG73;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope Between Brinell Hardness, Vickers Hardness, Rockwell
Hardness, Rockwell Superficial Hardness, and Knoop
1.1 This practice concerns tests in which solid specimens
Hardness)
are eroded or otherwise damaged by repeated discrete impacts
E177 Practice for Use of the Terms Precision and Bias in
of liquid drops or jets. Among the collateral forms of damage
ASTM Test Methods
considered are degradation of optical properties of window
E179 Guide for Selection of Geometric Conditions for
materials, and penetration, separation, or destruction of coat-
MeasurementofReflectionandTransmissionPropertiesof
ings. The objective of the tests may be to determine the
Materials
resistance to erosion or other damage of the materials or
G1 Practice for Preparing, Cleaning, and Evaluating Cor-
coatings under test, or to investigate the damage mechanisms
rosion Test Specimens
and the effect of test variables. Because of the specialized
G32 Test Method for Cavitation Erosion Using Vibratory
natureofthesetestsandthedesireinmanycasestosimulateto
Apparatus
some degree the expected service environment, the promulga-
G40 Terminology Relating to Wear and Erosion
tion of a method is not deemed practicable.This practice gives
G134 Test Method for Erosion of Solid Materials by a
guidance in setting up a test, and specifies test and analysis
Cavitating Liquid Jet
procedures and reporting requirements that can be followed
2.2 Military Standards:
even with quite widely differing materials, test facilities, and
MIL-C-83231 Coatings, Polyurethane, Rain Erosion Resis-
test conditions. It also provides a standardized scale of erosion
tance for Exterior Aircraft and Missile Plastic Parts
resistance numbers applicable to metals and other structural
MIL-P-8184 Plastic Sheet, Acrylic, Modified
materials.
1.2 The values stated in SI units are to be regarded as
3. Terminology
standard.The inch-pound units in parentheses are provided for
3.1 See Terminology G 40 for definitions of terms relating
information.
to erosion by liquids and solids. Important terms used in this
1.3 This standard does not purport to address all of the
practice, or that might be used in a test report following this
safety concerns, if any, associated with its use. It is the
practice,aredefinedineither3.2or3.3.Definitionsofselected
responsibility of the user of this standard to establish appro-
terms quoted from Terminology G40 are listed in 3.2. Defini-
priate safety and health practices and determine the applica-
tions of terms specific to this practice are presented in 3.3.
bility of regulatory limitations prior to use.
3.2 Definitions—All definitions listed below are quoted
2. Referenced Documents from Terminology G40–98.
3.2.1 acceleration period, n— in cavitation and liquid
2.1 ASTM Standards:
impingement erosion, the stage following the incubation pe-
D1003 Test Method for Haze and LuminousTransmittance
2 riod, during which the erosion rate increases from near zero to
of Transparent Plastics
a maximum value. (See also erosion rate-time.)
E92 Test Method for Vickers Hardness of Metallic Mate-
3.2.2 angle of incidence, n— in impingement erosion, the
rials
anglebetweenthedirectionofmotionofanimpingingliquidor
E140 HardnessConversionTablesforMetals(Relationship
solid particle and the normal to the surface at the point of
impact.
This practice is under the jurisdiction of ASTM Committee G-2 on Wear and
Erosion and is the direct responsibility of Subcommittee G02.10 on Erosion by
Solids and Liquids. Annual Book of ASTM Standards, Vol 14.02.
Current edition approved Apr. 10, 1998. Published November 1998. Originally Annual Book of ASTM Standards, Vol 06.01.
published as G73–82. Last previous edition G73–93. Annual Book of ASTM Standards, Vol 03.02.
2 7
Annual Book of ASTM Standards, Vol 08.01. AvailablefromStandardizationDocumentsOrderDesk,Bldg.4SectionD,700
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Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
G73–98
3.2.3 attenuation period, n— in cavitation and liquid im- cavitation erosion, liquid impingement erosion, solid impinge-
pingement erosion, a less-preferred term for deceleration ment erosion, beach erosion, etc.
period.
3.2.11 erosion rate, n—anydeterminationoftherateofloss
3.2.4 catastrophic period, n— in cavitation or liquid im-
of material (erosion) with exposure duration. (See also ratio-
pingement erosion, a stage during which the erosion rate
nalized erosion rate.)
increases so drastically that continued exposure threatens or
3.2.11.1 Discussion—Erosion rate is usually determined as
causesgrossdisintegrationoftheexposedsurface.Thisstageis
a slope on the cumulative erosion-time curve. Since in cavita-
not inevitable; it is observed most commonly with some brittle
tionorliquidimpingementthiscurveisgenerallynotastraight
materials.Whenitdoesoccur,itmaybeginduringanystageof
line, it is necessary to specify how any particular numerical
the more common erosion rate-time pattern.
value was determined from this curve. The following more
3.2.5 cumulative erosion, n— in cavitation and impinge-
explicittermsmaybeused:averageerosionrate,instantaneous
ment erosion, the total amount of material lost from a solid
erosion rate, interval erosion rate, maximum erosion rate, and
surfaceduringallexposureperiodssinceitwasfirstexposedto
terminal erosion rate. See individual definitions of these terms.
cavitation or impingement as a newly finished surface. (More
3.2.12 erosion rate-time curve, n—a plot of instantaneous
specific terms that may be used are cumulative mass loss,
erosion rate versus exposure duration, usually obtained by
cumulative volume loss,or cumulative mean depth of erosion.
numerical or graphical differentiation of the cumulative
See also cumulative erosion-time curve.)
erosion-time curve. (See also erosion rate-time pattern.)
3.2.5.1 Discussion—Unless otherwise indicated by the con-
3.2.13 erosionrate-timepattern,n—anyqualitativedescrip-
text, it is implied that the conditions of cavitation or impinge-
tion of the shape of the erosion rate-time curve, in terms of the
ment have remained the same throughout all exposure periods,
several stages of which it may be composed.
with no intermediate refinishing of the surface.
3.2.13.1 Discussion—In cavitation and liquid impingement
3.2.6 cumulative erosion-time curve, n—in cavitation and
erosion, a typical pattern may be composed of all or some of
impingement erosion, a plot of cumulative erosion versus
the following “periods” or “stages”: incubation period, accel-
cumulative exposure duration, usually determined by periodic
eration period, maximum-rate period, deceleration period,
interruption of the test and weighing of the specimen. This is
terminal period, and occasionally catastrophic period. The
the primary record of an erosion test. Most other characteris-
generic term“ period” is recommended when associated with
tics, such as the incubation period, maximum erosion rate,
quantitativemeasuresofitsduration,etc.;forpurelyqualitative
terminal erosion rate, and erosion rate-time curve, are derived
descriptions the term “stage” is preferred.
from it.
3.2.14 exposure duration, n— in erosion or wear, exposure
3.2.7 damage, n—in cavitation or impingement, any effect
time, or any other appropriate measure of the accumulation of
on a solid body resulting from its exposure to these phenom-
exposure to an erosion or wear environment.
ena.This may include loss of material, surface deformation, or
3.2.14.1 Discussion—For impingement erosion, some alter-
anyotherchangesinmicrostructure,properties,orappearance.
nativedurationparametersarethenumberofimpactsthathave
3.2.7.1 Discussion—This term as here defined should nor-
occurred on a given point, or the mass or volume of particles
mally be used with the appropriate modifier, for example,
thathaveimpingedonaunitareaofexposedsurface.Forwear,
“cavitation damage,” “liquid impingement damage,” “single-
it may be the distance traveled.
impact damage,” and so forth.
3.2.15 impact velocity, n— in impingement erosion, the
3.2.8 deceleration period, n— in cavitation or liquid im-
relative velocity between the surface of a solid body and an
pingement erosion, the stage following the acceleration period
impinging liquid or solid particle.
or the maximum rate period (if any), during which the erosion
rate has an overall decreasing trend although fluctuations may 3.2.15.1 Discussion—To describe this velocity completely,
it is necessary to specify the direction of motion of the particle
be superimposed on it. (See also erosion rate—time pattern.)
relative to the solid surface in addition to the magnitude of the
3.2.9 distributed impact test, n— in impingement erosion
velocity. The following related terms are also in use:
testing, an apparatus or method that produces a spatial distri-
(1) absolute impact velocity—the magnitude of the impact
bution of impacts by liquid or solid bodies over an exposed
velocity.
surface of a specimen.
(2) normal impact velocity—the component of the impact
3.2.9.1 Discussion—Examples of such tests are those em-
velocity that is perpendicular to the surface of the test solid at
ploying liquid sprays or simulated rainfields. If the impacts are
the point of impact.
distributed uniformly over the surface, the term “uniformly
3.2.16 impingement, n— in tribology, a process resulting in
distributed impact test” may be used. (Contrast with repetitive
impact erosion test.) a continuing succession of impacts between (liquid or solid)
particles and a solid surface.
3.2.10 erosion, n—in tribology, progressive loss of original
material from a solid surface due to mechanical interaction
3.2.16.1 Discussion—In preferred usage, “impingement”
between that surface and a fluid, a multicomponent fluid, or
also connotes that the impacting particles are smaller than the
impinging liquid or solid particles.
solid surface, and that the impacts are distributed over that
3.2.10.1 Discussion—Because of the broad scope of this surfaceoraportionofit.Ifallimpactsaresuperimposedonthe
term, it is recommended that it normally be qualified to same point or zone, then the term“ repeated impact” is
indicate the relevant mechanism or context, for example, preferred.
G73–98
3.2.16.2 Discussion—In other contexts, the term “impinge- analyzed. By “similarly analyzed” is meant that the two
ment” sometimes has different meanings, as in the steady-state erosionratesmustbedeterminedforcorrespondingportionsof
impingement of a liquid stream against a solid body, or in the erosion rate-time pattern; for instance, the maximum
“impingement corrosion.” The definition given here applies in erosion rate or the terminal erosion rate.
the context of Committee G-2’s scope.
3.2.26.1 Discussion—A recommended complete wording
3.2.17 impingement corrosion, n—a form of erosion-
has the form, “The normalized erosion resistance of (test
corrosion generally associated with the impingement of a material) relative to (reference material) based on (criterion of
high-velocity, flowing liquid containing air bubbles against a data analysis) is (numerical value).”
solid surface.
3.2.27 normalized incubation resistance, N , n—in cavita-
3.2.18 incubation period, n— in cavitation and impinge- tion and liquid impingement erosion, the incubation period of
ment erosion, the initial stage of the erosion rate-time pattern
a test material, divided by the incubation period of a specified
duringwhichtheerosionrateiszeroornegligiblecomparedto referencematerialsimilarlytestedandsimilarlyanalyzed.(See
later stages. Also, the exposure duration associated with this
also normalized erosion resistance.)
stage. (Quantitatively it is sometimes defined as the intercept
3.2.28 rationalized erosion rate, n—an erosion rate for
on the time or exposure axis, of a straight line extension of the
impingementtestsexpressedindimensionlessformasfollows:
maximum-slopeportionofthecumulativeerosion-timecurve.)
the volume of material lost per unit volume of (liquid or solid)
3.2.19 instantaneous erosion rate, n—the slope of a tangent particles impinging, both determined for the same area.
tothecumulativeerosion-timecurveataspecifiedpointonthat
3.2.29 repetitive impact erosion test, n—in impingement
curve.
erosion testing, an apparatus or method that produces a
3.2.20 liquid impingement erosion, n—progressive loss of
controlled or countable number of impacts by liquid or solid
original material from a solid surface due to continued expo- particles,ofuniformsize,shape,andimpactvelocity,allonthe
sure to impacts by liquid drops or jets. same location of the test specimen. One example of such a test
3.2.21 liquid jet, n—a body of liquid projected into motion, is the “wheel-and-jet” type of liquid impact apparatus.
usually of approximately cylindrical shape, such as could be 3.2.30 terminal erosion rate, n— in cavitation or liquid
producedbydischargingtheliquidthroughanorifice.Inliquid
impingement, the final steady-state erosion rate that is reached
impingement testing two kinds of liquid jet are used: (or appears to be approached asymptotically) after the erosion
3.2.21.1 continuous jet—a continuous flow of liquid in the rate has declined from its maximum value. (See also terminal
form of a jet. period and erosion rate–time pattern.)
3.2.31 terminal period, n— in cavitation or liquid impinge-
3.2.21.2 slug, or jet segment—a body of liquid projected
into motion, in the form approximately of a finite cylinder ment erosion, a stage following the deceleration period, during
which the erosion rate has levelled off and remains approxi-
whoselengthisusuallynomorethanseveraltimesitsdiameter
and which moves in a direction approximately parallel to its matelyconstant(sometimeswithsuperimposedfluctuations)at
length. a value substantially lower than the maximum rate attained
earlier. This occurs in some, but not all, cavitation and liquid
3.2.22 maximum erosion rate, n— in cavitation and liquid
impingement tests. (See also erosion rate–time pattern.)
impingement,themaximuminstantaneouserosionrateinatest
that exhibits such a maximum followed by decreasing erosion 3.3 Definitions of Terms Specific to This Standard:
rates. (See also erosion rate–time pattern.)
3.3.1 appa
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