ASTM E963-95(2010)
(Practice)Standard Practice for Electrolytic Extraction of Phases from Ni and Ni-Fe Base Superalloys Using a Hydrochloric-Methanol Electrolyte
Standard Practice for Electrolytic Extraction of Phases from Ni and Ni-Fe Base Superalloys Using a Hydrochloric-Methanol Electrolyte
SIGNIFICANCE AND USE
This practice can be used to extract carbides, borides, TCP and GCP phases, which can then be qualitatively or quantitatively analyzed by X-ray diffraction or microanalysis.
Careful control of parameters is necessary for reproducible quantitative results. Within a given laboratory, such results can be obtained routinely; however, caution must be exercised when comparing quantitative results from different laboratories.
Comparable qualitative results can be obtained routinely among different laboratories using this procedure.
SCOPE
1.1 This practice covers a procedure for the isolation of carbides, borides, TCP (topologically close-packed), and GCP (geometrically close-packed) phases (Note 1) in nickel and nickel-iron base gamma prime strengthened alloys. Contamination of the extracted residue by coarse matrix (gamma) or gamma prime particles, or both, reflects the condition of the alloy rather than the techniques mentioned in this procedure.
1.2 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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Designation: E963 − 95 (Reapproved 2010)
Standard Practice for
Electrolytic Extraction of Phases from Ni and Ni-Fe Base
Superalloys Using a Hydrochloric-Methanol Electrolyte
This standard is issued under the fixed designation E963; 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 3. Significance and Use
1.1 This practice covers a procedure for the isolation of 3.1 This practice can be used to extract carbides, borides,
carbides, borides, TCP (topologically close-packed), and GCP TCP and GCP phases, which can then be qualitatively or
(geometrically close-packed) phases (Note 1) in nickel and quantitatively analyzed by X-ray diffraction or microanalysis.
nickel-iron base gamma prime strengthened alloys. Contami-
3.2 Careful control of parameters is necessary for reproduc-
nation of the extracted residue by coarse matrix (gamma) or
ible quantitative results.Within a given laboratory, such results
gamma prime particles, or both, reflects the condition of the
can be obtained routinely; however, caution must be exercised
alloy rather than the techniques mentioned in this procedure.
when comparing quantitative results from different laborato-
1.2 This standard does not purport to address all of the
ries.
safety concerns, if any, associated with its use. It is the
3.3 Comparablequalitativeresultscanbeobtainedroutinely
responsibility of the user of this standard to establish appro- 3
among different laboratories using this procedure.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. (See 3.3.2.1 and
4. Apparatus
4.1.1.)
4.1 Cell or Container for Electrolyte— A glass vessel of
NOTE 1—Ni Ti (eta phase) has been found to be soluble in the
about 400-mL capacity is recommended. For the sample size
electrolyte for some alloys.
and current density recommended later in this procedure,
electrolysis can proceed up to about 4 h, and up to about4gof
2. Terminology
alloy can be dissolved in 250 mL of electrolyte without
2.1 Definitions:
exceeding a metallic ion concentration of 16 g/L. Above this
2.1.1 extraction cell—laboratory apparatus consisting of a
concentration, cathode plating has been observed to be more
beaker to contain the electrolyte, a dc power supply, a noble
likely to occur. A mechanism for cooling the electrolyte is
metal sheet or screen cathode and a noble metal wire basket or
recommended. For example, an ice water bath or water-
wire to affix to the sample (anode).
jacketed cell may be used to keep the electrolyte between 0°
2.1.2 geometrically close-packed (GCP) phases—
and 30°C.
precipitated phases found in nickel-base alloys that have the
4.2 Cathode—Material must be inert during electrolysis.
form A B, where B is a smaller atom than A. In superalloys,
Tantalum and platinum sheet or mesh are known to meet this
these are the common FCC Ni (Al, Ti) or occasionally found
requirement. Use of a single wire is to be avoided, since
HCP Ni Ti.
cathode surface area should be larger than that of sample.
2.1.3 topologically close-packed (TCP) phases— precipi-
Distance between sample and cathode should be as great as
tated phases in nickel-base alloys, characterized as composed
possible, within the size of cell chosen. For example, a sample
of close-packed layers of atoms forming in basket weave nets
with a surface area of 15 cm should have no side closer than
aligned with the octahedral planes of the FCC γ matrix. These
1.2 cm to the cathode. If the cell is cylindrical, as for the case
generally detrimental phases appear as thin plates, often
ofabeakerortheupperpartofaseparatoryfunnel,thecathode
nucleating on grain-boundary carbides. TCPphases commonly
could be curved to fit the inner cell wall to facilitate correct
found in nickel alloys are σ, µ , and Laves.
sample-cathode distance. The sample would then be centered
1 2
This practice is under the jurisdiction of ASTM Committee E04 on Metallog- Donachie, M. J. Jr., and Kriege, O. H., “Phase Extraction and Analysis in
raphy and is the direct responsibility of Subcommittee E04.11 on X-Ray and Superalloys—Summary of Investigations byASTM Committee E-4 Task Group I,”
Electron Metallography. Journal of Materials , Vol 7, 1972, pp. 269–278.
Current edition approved April 1, 2010. Published May 2010. Originally Donachie, M. J. Jr., “Phase Extraction and Analysis in Superalloys—Second
approved in 1983. Last previous edition approved in 2004 as E963 – 95 (2004). Summary of Investigations by ASTM Subcommittee E04.91,” Journal of Testing
DOI: 10.1520/E0963-95R10. and Evaluation, Vol 6, No. 3, 1978, pp. 189–195.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E963 − 95 (2010)
FIG. 1 Schematic Diagram of Extraction Cell
within the cell at the same height as the cathode. The cathode 4.5 Membrane Filter—Must be solvent and electrolyte
need not make a complete ring around the sample nor be more resistant, with pore size of 0.4 to 0.8 µm. Filters made of
than 5 cm high. poly(vinyl chloride) (fibrous) or polycarbonate (nonfibrous)
meet these requirements and are available commercially, as are
4.3 Anode—The sample must be suspended in the electro-
suitable filter holder assemblies. Mass loss for these materials
lyte by a material that is inert during electrolysis. Anode
in 10 % HCl-methanol is 10 %. The 2.5-cm diameter size is
connection material should be cleaned to prevent any contami-
useful for preparing the residue for the X-ray diffractometer,
nating material from falling into the cell. Good electrical
which is commonly used for phase analysis of the residue.
contact should be maintained between the sample wire and the
Otherwise, filter diameter is not critical. Filters should be
permanent anode wire from the dc power supply.Two methods
handled with blunt tweezers.
are found to be successful. Either method is subject to
disconnection of the sample due to shrinkage, which puts a 4.6 Centrifuge—Centrifuging for residue collection can be
limit on the electrolysis time: performed as an alternate to microfiltration.
4.3.1 Suspend the sample by platinum or platinum-rhodium
4.7 Balance—If quantitative analysis is desired, a balance
thermocouple wire (20 gauge) wrapped around it to form a
sensitive to 0.0001 g is required.
basket. To avoid a shielding problem, the ratio of sample area
covered by the wire to the exposed sample area should be
5. Reagents
small.
5.1 Electrolyte—Add and mix 1 part of 12 N hydrochloric
4.3.1.1 Mechanically attach or spot weld the platinum or
acid (sp gr 1.19) to 9 parts of absolute methyl alcohol by
platinum-rhodium thermocouple wire to the sample.
volume to make a 10 % HCl-methanol solution. For alloys
4.3.2 If the weld is not immersed, non-inert wire may be
containing W, Nb, Ta, or Hf, add one part by weight tartaric or
substituted; for example, chromel, nichrome, 300 series stain-
citric acid to 100 parts by volume HCl-methanol to make an
less steel, etc. Stop-off lacquer should be used below the
approximately 1 % tartaric or citric acid solution. All reagents
meniscus to maintain constant electrolyte level. This also
should be of at least ACS reagent grade quality.
eliminates formation of insoluble deposits immediately above
5.1.1 Warning—Add hydrochloric acid to absolute methyl
the meniscus and prevents arcing.
alcohol slowly and with constant stirring; otherwise sufficient
4.3.2.1 Warning—Care must be taken to prevent arcing
heat is generated to cause a hazardous condition. Mixing must
between anode and cathode which could ignite the methanol.
be done in an exhaust hood, because the fumes are toxic.
4.4 Power Supply—A variable dc power supply capable of
5.2 Sample and Residue Rinse—Absolute methyl alcohol is
providing 0 to 5 V is needed to obtain currents from 0 to 1.2A
to be used.
depending on total surface area of the sample. For example, a
sample with total surface area of 15 cm , electrolyzed at a
6. Procedure
current density of 0.1 A/cm , requires:
6.1 Sample Size and Geometry—A cube, cylinder, or rect-
2 2
15 cm 30.1 A/cm 5 1.2 A (1)
angular prism is preferred. Ideally, constant density should be
4.4.1 Current and voltage fluctuation should be no more maintained during electrolysis. Flattened samples, especially
than 65%. A 65 % current fluctuation represents a current thin sheet, will experience considerable shrinkage due to edge
density fluctuation of about 65 % which, for samples under 15 effects and current density increase as the electrolysis pro-
cm total surface area, is less than or equal to one-half the ceeds.Acube approximately 1.6 cm on a side will have a total
current density shift due to sample shrinkage over 4 h. surface area of approximately 15 cm . Smaller samples have
Potentiostatic control is not necessary, but may be helpful for larger increases in current density during constant current
determining optimum current density when setting up proce- electrolysisduetoshrinkage.Largersamplesmayrequiremore
dures for a new alloy. than 250 mL of ele
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