ASTM E963-95(2004)
(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.2
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.3
Comparable qualitative results can be obtained routinely among different laboratories using this procedure.3
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 0) 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.
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. (See 3.3.2.1 and 4.1.1.)
Note 1
Ni3 Ti (eta phase) has been found to be soluble in the electrolyte for some alloys.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information.
Designation:E963–95(Reapproved 2004)
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- among different laboratories using this procedure.
priate safety and health practices and determine the applica-
4. Apparatus
bility of regulatory limitations prior to use. (See 3.3.2.1 and
4.1.1.) 4.1 Cell or Container for Electrolyte— A glass vessel of
about 400-mL capacity is recommended. For the sample size
NOTE 1—Ni Ti (eta phase) has been found to be soluble in the
and current density recommended later in this procedure,
electrolyte for some alloys.
electrolysis can proceed up to about 4 h, and up to about4gof
2. Terminology alloy can be dissolved in 250 mL of electrolyte without
exceeding a metallic ion concentration of 16 g/L. Above this
2.1 Definitions:
concentration, cathode plating has been observed to be more
2.1.1 extraction cell—laboratory apparatus consisting of a
likely to occur. A mechanism for cooling the electrolyte is
beaker to contain the electrolyte, a dc power supply, a noble
recommended. For example, an ice water bath or water-
metal sheet or screen cathode and a noble metal wire basket or
jacketed cell may be used to keep the electrolyte between 0°
wire to affix to the sample (anode).
and 30°C.
2.1.2 geometrically close-packed (GCP) phases—
4.2 Cathode—Material must be inert during electrolysis.
precipitated phases found in nickel-base alloys that have the
Tantalum and platinum sheet or mesh are known to meet this
form A B, where B is a smaller atom than A. In superalloys,
requirement. Use of a single wire is to be avoided, since
these are the common FCC Ni (Al, Ti) or occasionally found
cathode surface area should be larger than that of sample.
HCP Ni Ti.
Distance between sample and cathode should be as great as
2.1.3 topologically close-packed (TCP) phases— precipi-
possible, within the size of cell chosen. For example, a sample
tated phases in nickel-base alloys, characterized as composed
with a surface area of 15 cm should have no side closer than
of close-packed layers of atoms forming in basket weave nets
1.2 cm to the cathode. If the cell is cylindrical, as for the case
aligned with the octahedral planes of the FCC g matrix. These
ofabeakerortheupperpartofaseparatoryfunnel,thecathode
generally detrimental phases appear as thin plates, often
could be curved to fit the inner cell wall to facilitate correct
nucleating on grain-boundary carbides. TCPphases commonly
sample-cathode distance. The sample would then be centered
found in nickel alloys are s, µ , and Laves.
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 Nov. 1, 2004. Published November 2004. Originally Donachie, M. J. Jr., “Phase Extraction and Analysis in Superalloys—Second
approved in 1983. Last previous edition approved in 2000 as E963 – 83 (2000). Summary of Investigations by ASTM Subcommittee E04.91,” Journal of Testing
DOI: 10.1520/E0963-95R04. 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 (2004)
FIG. 1 Schematic Diagram of Extraction Cell
within the cell at the same height as the cathode. The cathode poly(vinyl chloride) (fibrous) or polycarbonate (nonfibrous)
need not make a complete ring around the sample nor be more meet these requirements and are available commercially, as are
than 5 cm high. suitable filter holder assemblies. Mass loss for these materials
4.3 Anode—The sample must be suspended in the electro- in 10 % HCl-methanol is 10 %. The 2.5-cm diameter size is
lyte by a material that is inert during electrolysis. Anode useful for preparing the residue for the X-ray diffractometer,
connection material should be cleaned to prevent any contami- which is commonly used for phase analysis of the residue.
nating material from falling into the cell. Good electrical Otherwise, filter diameter is not critical. Filters should be
contact should be maintained between the sample wire and the handled with blunt tweezers.
permanent anode wire from the dc power supply.Two methods 4.6 Centrifuge—Centrifuging for residue collection can be
are found to be successful. Either method is subject to performed as an alternate to microfiltration.
disconnection of the sample due to shrinkage, which puts a 4.7 Balance—If quantitative analysis is desired, a balance
limit on the electrolysis time: sensitive to 0.0001 g is required.
4.3.1 Suspend the sample by platinum or platinum-rhodium
thermocouple wire (20 gauge) wrapped around it to form a
5. Reagents
basket. To avoid a shielding problem, the ratio of sample area
5.1 Electrolyte—Add and mix 1 part of 12 N hydrochloric
covered by the wire to the exposed sample area should be
acid (sp gr 1.19) to 9 parts of absolute methyl alcohol by
small.
volume to make a 10 % HCl-methanol solution. For alloys
4.3.1.1 Mechanically attach or spot weld the platinum or
containing W, Nb, Ta, or Hf, add one part by weight tartaric or
platinum-rhodium thermocouple wire to the sample.
citric acid to 100 parts by volume HCl-methanol to make an
4.3.2 If the weld is not immersed, non-inert wire may be
approximately 1 % tartaric or citric acid solution. All reagents
substituted; for example, chromel, nichrome, 300 series stain-
should be of at least ACS reagent grade quality.
less steel, etc. Stop-off lacquer should be used below the
5.1.1 Warning—Add hydrochloric acid to absolute methyl
meniscus to maintain constant electrolyte level. This also
alcohol slowly and with constant stirring; otherwise sufficient
eliminates formation of insoluble deposits immediately above
heat is generated to cause a hazardous condition. Mixing must
the meniscus and prevents arcing.
be done in an exhaust hood, because the fumes are toxic.
4.3.2.1 Warning—Care must be taken to prevent arcing
5.2 Sample and Residue Rinse—Absolute methyl alcohol is
between anode and cathode which could ignite the methanol.
to be used.
4.4 Power Supply—A variable dc power supply capable of
providing 0 to 5 V is needed to obtain currents from 0 to 1.2A
6. Procedure
depending on total surface area of the sample. For example, a
6.1 Sample Size and Geometry—A cube, cylinder, or rect-
sample with total surface area of 15 cm , electrolyzed at a
angular prism is preferred. Ideally, constant density should be
current density of 0.1 A/cm , requires:
maintained during electrolysis. Flattened samples, especially
2 2
15 cm 3 0.1 A/cm 5 1.2 A (1)
thin sheet, will experience considerable shrinkage due to edge
4.4.1 Current and voltage fluctuation should be no more effects and current density increase as the electrolysis pro-
than 65%. A 65 % current fluctuation represents a current ceeds.Acube approximately 1.6 cm on a side will have a total
density fluctuation of about 65 % which, for samples under 15 surface area of approximately 15 cm . Smaller samples have
cm total surface area, is less than or equal to one-half the larger increases in current density during constant current
current density shift due to sample shrinkage over 4 h. electrolysisduetoshrinkage.Largersamplesmayrequiremore
Potentiostatic control is not necessary, but may be helpful for than 250 mL of electrolyte and a power supply capable of
determining optimum current density when setting up proce- del
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.