ASTM E963-95(2000)
(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
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. (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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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: E 963 – 95 (Reapproved 2000)
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 E 963; 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 (e) 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 Comparable qualitative results can be obtained routinely
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
of a beaker or the upper part of a separatory funnel, the cathode
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. TCP phases commonly
found in nickel alloys are s, μ , and Laves.
Donachie, M. J. Jr., and Kriege, O. H., “Phase Extraction and Analysis in
This practice is under the jurisdiction of ASTM Committee E04 on Metallog- Superalloys—Summary of Investigations by ASTM Committee E-4 Task Group I,”
raphy and is the direct responsibility of Subcommittee E04.11 on X-Ray and Journal of Materials, Vol 7, 1972, pp. 269–278.
Electron Metallography. Donachie, M. J. Jr., “Phase Extraction and Analysis in Superalloys—Second
Current edition approved Jan. 15, 1995. Published March 1995. Originally Summary of Investigations by ASTM Subcommittee E04.91,” Journal of Testing
published as E 963 – 83. Last previous edition E963 – 83 (1989). 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.
E 963
FIG. 1 Schematic Diagram of Extraction Cell
sample-cathode distance. The sample would then be centered 4.5 Membrane Filter—Must be solvent and electrolyte re-
within the cell at the same height as the cathode. The cathode sistant, with pore size of 0.4 to 0.8 μm. Filters made of
need not make a complete ring around the sample nor be more poly(vinyl chloride) (fibrous) or polycarbonate (nonfibrous)
than 5 cm high. 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 4.6 Centrifuge—Centrifuging for residue collection can be
disconnection of the sample due to shrinkage, which puts a
performed as an alternate to microfiltration.
limit on the electrolysis time: 4.7 Balance—If quantitative analysis is desired, a balance
4.3.1 Suspend the sample by platinum or platinum-rhodium
sensitive to 0.0001 g is required.
thermocouple wire (20 gauge) wrapped around it to form a
basket. To avoid a shielding problem, the ratio of sample area
5. Reagents
covered by the wire to the exposed sample area should be
5.1 Electrolyte—Add and mix 1 part of 12 N hydrochloric
small.
acid (sp gr 1.19) to 9 parts of absolute methyl alcohol by
4.3.1.1 Mechanically attach or spot weld the platinum or
volume to make a 10 % HCl-methanol solution. For alloys
platinum-rhodium thermocouple wire to the sample.
containing W, Nb, Ta, or Hf, add one part by weight tartaric or
4.3.2 If the weld is not immersed, non-inert wire may be
citric acid to 100 parts by volume HCl-methanol to make an
substituted; for example, chromel, nichrome, 300 series stain-
approximately 1 % tartaric or citric acid solution. All reagents
less steel, etc. Stop-off lacquer should be used below the
should be of at least ACS reagent grade quality.
meniscus to maintain constant electrolyte level. This also
5.1.1 Warning—Add hydrochloric acid to absolute methyl
eliminates formation of insoluble deposits immediately above
alcohol slowly and with constant stirring; otherwise sufficient
the meniscus and prevents arcing.
heat is generated to cause a hazardous condition. Mixing must
4.3.2.1 Warning—Care must be taken to prevent arcing
be done in an exhaust hood, because the fumes are toxic.
between anode and cathode which could ignite the methanol.
5.2 Sample and Residue Rinse—Absolute methyl alcohol is
4.4 Power Supply—A variable dc power supply capable of
to be used.
providing 0 to 5 V is needed to obtain currents from 0 to 1.2 A
depending on total surface area of the sample. For example, a
6. Procedure
sample with total surface area of 15 cm , electrolyzed at a
6.1 Sample Size and Geometry—A cube, cylinder, or rect-
current density of 0.1 A/cm , requires:
angular prism is preferred. Ideally, constant density should be
2 2
15 cm 3 0.1 A/cm 5 1.2 A (1)
maintained during electrolysis. Flattened samples, especially
4.4.1 Current and voltage fluctuation should be no more thin sheet, will experience considerable shrinkage due to edge
than 65%. A 65 % current fluctuation represents a current effects and current density increase as the electrolysis pro-
density fluctuation of about 65 % which, for samples under 15 ceeds. A cube approximately 1.6 cm on a side will have a total
2 2
cm total surface area, is less than or equal to one-half the surface area of approximately 15 cm . Smaller samples have
current density shift due to sample shrinkage over 4 h. larger increases in current density during constant current
Potentiostatic control is not necessary, but may be helpful for electrolysis due to shrinkage. Larger samples may require more
determining optimum current density when setting up pr
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.