ASTM G32-16(2021)e1
(Test Method)Standard Test Method for Cavitation Erosion Using Vibratory Apparatus
Standard Test Method for Cavitation Erosion Using Vibratory Apparatus
SIGNIFICANCE AND USE
5.1 This test method may be used to estimate the relative resistance of materials to cavitation erosion as may be encountered, for instance, in pumps, hydraulic turbines, hydraulic dynamometers, valves, bearings, diesel engine cylinder liners, ship propellers, hydrofoils, and in internal flow passages with obstructions. An alternative method for similar purposes is Test Method G134, which employs a cavitating liquid jet to produce erosion on a stationary specimen. The latter may be more suitable for materials not readily formed into a precisely shaped specimen. The results of either, or any, cavitation erosion test should be used with caution; see 5.8.
5.2 Some investigators have also used this test method as a screening test for materials subjected to liquid impingement erosion as encountered, for instance, in low-pressure steam turbines and in aircraft, missiles or spacecraft flying through rainstorms. Test Method G73 describes another testing approach specifically intended for that type of environment.
5.3 This test method is not recommended for evaluating elastomeric or compliant coatings, some of which have been successfully used for protection against cavitation or liquid impingement of moderate intensity. This is because the compliance of the coating on the specimen may reduce the severity of the liquid cavitation induced by its vibratory motion. The result would not be representative of a field application, where the hydrodynamic generation of cavitation is independent of the coating.
Note 1: An alternative approach that uses the same basic apparatus, and is deemed suitable for compliant coatings, is the “stationary specimen” method. In that method, the specimen is fixed within the liquid container, and the vibrating tip of the horn is placed in close proximity to it. The cavitation “bubbles” induced by the horn (usually fitted with a highly resistant replaceable tip) act on the specimen. While several investigators have used this approach (see X4.2....
SCOPE
1.1 This test method covers the production of cavitation damage on the face of a specimen vibrated at high frequency while immersed in a liquid. The vibration induces the formation and collapse of cavities in the liquid, and the collapsing cavities produce the damage to and erosion (material loss) of the specimen.
1.2 Although the mechanism for generating fluid cavitation in this method differs from that occurring in flowing systems and hydraulic machines (see 5.1), the nature of the material damage mechanism is believed to be basically similar. The method therefore offers a small-scale, relatively simple and controllable test that can be used to compare the cavitation erosion resistance of different materials, to study in detail the nature and progress of damage in a given material, or—by varying some of the test conditions—to study the effect of test variables on the damage produced.
1.3 This test method specifies standard test conditions covering the diameter, vibratory amplitude and frequency of the specimen, as well as the test liquid and its container. It permits deviations from some of these conditions if properly documented, that may be appropriate for some purposes. It gives guidance on setting up a suitable apparatus and covers test and reporting procedures and precautions to be taken. It also specifies standard reference materials that must be used to verify the operation of the facility and to define the normalized erosion resistance of other test materials.
1.4 A history of this test method is given in Appendix X4, followed by a comprehensive bibliography.
1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.
1.6 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...
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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.
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Designation: G32 − 16 (Reapproved 2021)
Standard Test Method for
Cavitation Erosion Using Vibratory Apparatus
ThisstandardisissuedunderthefixeddesignationG32;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Caution statement in 9.1.1.5 changed to warning editorially and editorial changes made throughout in June 2021
1. Scope responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
1.1 This test method covers the production of cavitation
mine the applicability of regulatory limitations prior to use.
damage on the face of a specimen vibrated at high frequency
For specific safety warning information, see 6.1, 10.3, and
while immersed in a liquid. The vibration induces the forma-
10.6.1.
tion and collapse of cavities in the liquid, and the collapsing
1.7 This international standard was developed in accor-
cavities produce the damage to and erosion (material loss) of
dance with internationally recognized principles on standard-
the specimen.
ization established in the Decision on Principles for the
1.2 Although the mechanism for generating fluid cavitation
Development of International Standards, Guides and Recom-
in this method differs from that occurring in flowing systems
mendations issued by the World Trade Organization Technical
and hydraulic machines (see 5.1), the nature of the material
Barriers to Trade (TBT) Committee.
damage mechanism is believed to be basically similar. The
method therefore offers a small-scale, relatively simple and
2. Referenced Documents
controllable test that can be used to compare the cavitation
2.1 ASTM Standards:
erosion resistance of different materials, to study in detail the
A276/A276MSpecification for Stainless Steel Bars and
nature and progress of damage in a given material, or—by
Shapes
varying some of the test conditions—to study the effect of test
B160Specification for Nickel Rod and Bar
variables on the damage produced.
B211/B211MSpecification for Aluminum and Aluminum-
1.3 This test method specifies standard test conditions
Alloy Rolled or Cold Finished Bar, Rod, and Wire
covering the diameter, vibratory amplitude and frequency of
D1193Specification for Reagent Water
the specimen, as well as the test liquid and its container. It
E177Practice for Use of the Terms Precision and Bias in
permits deviations from some of these conditions if properly
ASTM Test Methods
documented, that may be appropriate for some purposes. It
E691Practice for Conducting an Interlaboratory Study to
gives guidance on setting up a suitable apparatus and covers
Determine the Precision of a Test Method
test and reporting procedures and precautions to be taken. It
E960Specification for Laboratory Glass Beakers
also specifies standard reference materials that must be used to
G40Terminology Relating to Wear and Erosion
verifytheoperationofthefacilityandtodefinethenormalized
G73Test Method for Liquid Impingement Erosion Using
erosion resistance of other test materials.
Rotating Apparatus
G117Guide for Calculating and Reporting Measures of
1.4 A history of this test method is given in Appendix X4,
followed by a comprehensive bibliography. Precision Using Data from Interlaboratory Wear or Ero-
sion Tests (Withdrawn 2016)
1.5 The values stated in SI units are to be regarded as
G119Guide for Determining Synergism Between Wear and
standard. The values given in parentheses after SI units are
Corrosion
providedforinformationonlyandarenotconsideredstandard.
G134Test Method for Erosion of Solid Materials by Cavi-
1.6 This standard does not purport to address all of the
tating Liquid Jet
safety concerns, if any, associated with its use. It is the
1 2
This test method is under the jurisdiction of ASTM Committee G02 on Wear For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and Erosion and is the direct responsibility of Subcommittee G02.10 on Erosion by contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Solids and Liquids. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved June 1, 2021. Published June 2021. Originally the ASTM website.
approved in 1972. Last previous edition approved in 2016 as G32–16. DOI: The last approved version of this historical standard is referenced on
10.1520/G0032-16R21E01. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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G32 − 16 (2021)
3. Terminology 3.1.9.1 Discussion—In cavitation and liquid impingement
erosion, a typical pattern may be composed of all or some of
3.1 Definitions:
the following “periods” or “stages”: incubation period, accel-
3.1.1 See Terminology G40 for definitions of terms relating
eration period, maximum-rate period, deceleration period,
to cavitation erosion. For convenience, important definitions
terminal period, and occasionally catastrophic period. The
forthistestmethodarelistedbelow;someareslightlymodified
generic term “period” is recommended when associated with
from Terminology G40 or not contained therein.
quantitativemeasuresofitsduration,etc.;forpurelyqualitative
3.1.2 average erosion rate, n—a less preferred term for
descriptions the term“ stage” is preferred.
cumulative erosion rate.
3.1.10 erosion threshold time, n—the exposure time re-
3.1.3 cavitation, n—the formation and subsequent collapse,
quired to reach a mean depth of erosion of 1.0 µm.
within a liquid, of cavities or bubbles that contain vapor or a
3.1.10.1 Discussion—Amean depth of erosion of 1.0 µm is
mixture of vapor and gas.
theleastaccuratelymeasurablevalueconsideringtheprecision
3.1.3.1 Discussion—In general, cavitation originates from a
of the scale, specimen diameter, and density of the standard
local decrease in hydrostatic pressure in the liquid, produced
reference material.
by motion of the liquid (see flow cavitation) or of a solid
boundary (see vibratory cavitation). It is distinguished in this 3.1.11 flow cavitation, n—cavitationcausedbyadecreasein
way from boiling, which originates from an increase in liquid local pressure induced by changes in velocity of a flowing
temperature. liquid, such as in flow around an obstacle or through a
3.1.3.2 Discussion—The term cavitation, by itself, should constriction.
not be used to denote the damage or erosion of a solid surface
3.1.12 incubation period, n—the initial stage of the erosion
that can be caused by it; this effect of cavitation is termed
rate-time pattern during which the erosion rate is zero or
cavitation damage or cavitation erosion. To erode a solid
negligible compared to later stages.
surface, bubbles or cavities must collapse on or near that
3.1.12.1 Discussion—The incubation period is usually
surface.
thought to represent the accumulation of plastic deformation
3.1.4 cavitation erosion, n—progressive loss of original
andinternalstressesunderthesurface,thatprecedessignificant
material from a solid surface due to continued exposure to
material loss. There is no exact measure of the duration of the
cavitation.
incubation period. See related terms, erosion threshold time
and nominal incubation period.
3.1.5 cumulative erosion, n—the total amount of material
lost from a solid surface during all exposure periods since it
3.1.13 maximum erosion rate, n—the maximum instanta-
was first exposed to cavitation or impingement as a newly
neous erosion rate in a test that exhibits such a maximum
finished surface. (More specific terms that may be used are
followed by decreasing erosion rates. (See also erosion rate-
cumulative mass loss, cumulative volume loss,or cumulative
time pattern.)
mean depth of erosion. See also cumulative erosion-time
3.1.13.1 Discussion—Occurrence of such a maximum is
curve.)
typical of many cavitation and liquid impingement tests. In
3.1.5.1 Discussion—Unless otherwise indicated by the
some instances it occurs as an instantaneous maximum, in
context, it is implied that the conditions of cavitation or
others as a steady-state maximum which persists for some
impingement have remained the same throughout all exposure
time.
periods, with no intermediate refinishing of the surface.
3.1.14 mean depth of erosion (MDE), n—the average thick-
3.1.6 cumulative erosion rate, n—the cumulative erosion at
ness of material eroded from a specified surface area, usually
a specified point in an erosion test divided by the correspond-
calculatedbydividingthemeasuredmasslossbythedensityof
ing cumulative exposure duration; that is, the slope of a line
the material to obtain the volume loss and dividing that by the
from the origin to the specified point on the cumulative
area of the specified surface. (Also known as mean depth of
erosion-time curve. (Synonym: average erosion rate)
penetration or MDP. Since that might be taken to denote the
3.1.7 cumulative erosion-time curve—a plot of cumulative average value of the depths of individual pits, it is a less
preferred term.)
erosion versus cumulative exposure duration, usually deter-
mined by periodic interruption of the test and weighing of the
3.1.15 nominalincubationtime,n—theinterceptonthetime
specimen. This is the primary record of an erosion test. Most
orexposureaxisofthestraight-lineextensionofthemaximum-
other characteristics, such as the incubation period, maximum
slope portion of the cumulative erosion-time curve; while this
erosionrate,terminalerosionrate,anderosionrate-timecurve,
is not a true measure of the incubation stage, it serves to locate
are derived from it.
the maximum erosion rate line on the cumulative erosion
3.1.8 erosion rate-time curve, n—a plot of instantaneous versus time coordinates.
erosion rate versus exposure duration, usually obtained by
3.1.16 normalized erosion resistance, N,n—a measure of
e
numerical or graphical differentiation of the cumulative
the erosion resistance of a test material relative to that of a
erosion-time curve. (See also erosion rate-time pattern.)
specifiedreferencematerial,calculatedbydividingthevolume
3.1.9 erosion rate-time pattern, n—any qualitative descrip- loss rate of the reference material by that of the test material,
tion of the shape of the erosion rate-time curve in terms of the when both are similarly tested and similarly analyzed. By
several stages of which it may be composed. “similarly analyzed” is meant that the two erosion rates must
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G32 − 16 (2021)
be determined for corresponding portions of the erosion rate shaped specimen. The results of either, or any, cavitation
time pattern; for instance, the maximum erosion rate or the erosion test should be used with caution; see 5.8.
terminal erosion rate.
5.2 Some investigators have also used this test method as a
3.1.16.1 Discussion—A recommended complete wording
screening test for materials subjected to liquid impingement
has the form, “The normalized erosion resistance of (test
erosion as encountered, for instance, in low-pressure steam
material) relative to (reference material) based on (criterion of
turbines and in aircraft, missiles or spacecraft flying through
data analysis) is (numerical value).”
rainstorms. Test Method G73 describes another testing ap-
3.1.17 normalized incubation resistance N ,n—thenominal
proach specifically intended for that type of environment.
o
incubation time of a test material, divided by the nominal
5.3 This test method is not recommended for evaluating
incubation time of a specified reference material similarly
elastomeric or compliant coatings, some of which have been
tested and similarly analyzed. (See also normalized erosion
successfully used for protection against cavitation or liquid
resistance.)
impingement of moderate intensity. This is because the com-
3.1.18 tangent erosion rate, n—the slope of a straight line
plianceofthecoatingonthespecimenmayreducetheseverity
drawn through the origin and tangent to the knee of the
of the liquid cavitation induced by its vibratory motion. The
cumulative erosion-time curve, when that curve has the char-
result would not be representative of a field application, where
acteristic S-shaped pattern that permits this. In such cases, the
the hydrodynamic generation of cavitation is independent of
tangent erosion rate also represents the maximum cumulative
the coating.
erosion rate exhibited during the test.
NOTE 1—An alternative approach that uses the same basic apparatus,
3.1.19 terminal erosion rate, n—the final steady-state ero-
and is deemed suitable for compliant coatings, is the “stationary speci-
sion rate that is reached (or appears to be approached asymp-
men” method. In that method, the specimen is fixed within the liquid
totically) after the erosion rate has declined from its maximum container, and the vibrating tip of the horn is placed in close proximity to
it. The cavitation “bubbles” induced by the horn (usually fitted with a
value.(Seealsoterminalperiodanderosionrate-timepattern.)
highly resistant replaceable tip) act on the specimen. While several
3.1.20 vibratory cavitation, n—cavitation caused by the
investigatorshaveusedthisapproach(seeX4.2.3),theyhavedifferedwith
pressure fluctuations within a liquid, induced by the vibration regard to standoff distances and other arrangements. The stationary
specimen approach can also be used for brittle materials which can not be
of a solid surface immersed in the liquid.
formed into a threaded specimen nor into a disc that can be cemented to
a threaded specimen, as required for this test method (see 7.6).
4. Summary of Test Method
5.4 This test method should not be directly used to rank
4.1 This test method generally utilizes a commercially
materials for applications where electrochemical corrosion or
obtained 20-kHz ultrasonic transducer to which is attached a
solid particle impingement plays a major role. However,
suitably designed “horn” or velocity transformer. A specimen
adaptations of the basic method and apparatus have been used
button of proper mass is attached by threading into the tip of
for such purposes (see 9.2.5, 9.2.6, and X4.2). Guide G119
the horn.
may be followed in order to determine the synergism between
4.2 The specimen is immersed into a container of the test the mechanical and electrochemical effects.
liquid (generally distilled water) that must be maintained at a
5.5 Those who are engaged in basic research, or concerned
specifiedtemperaturedu
...
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