A new metallographic procedure for edge retention of enclosed surfaces Page: 4 of 13
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
(2) rotary gold coating the inside diameter in a vacuum evaporator, (3) copper (Cu)
or nickel (Ni) electrolytic plating to build up a protective edge layer, (4) standard
pressure mounting in a hard thermosetting plastic Sie Epomet (registered trade-mark
of Buehler, Ltd.) at about 325 F for a few minutes and (5) polishing the mounted
sample so as to portray intact areas where the edges were preserved. The plating
material did not always retain adherence to the alloy and/or deposits on a particular
cross-section at enough areas to warrant study, necessitating numerous cross-
sectional preparations for a given tube sample. Figure 1 makes a general compari-
son with the new technique by showing a typical gap that resulted from the above
procedure using a copper plating solution. Nickel plates produced similar results,
and aN of these processes produced iquid solutions that incurred disposal costs.
Electroless deposits for us were even more unsatisfactory. Total sample preparation
time was found to be a little over nine hours per mount.
Work to preserve the deposits and the surface features of tubing with a metallic
material began with the use of Woods alloy, which contains bismuth (B), lead (Pb),
tin (Sn), and cadmium (Cd) and melts rather low at 158 F, considering potential
heat-up during sample preparation. A number of others with 50 weight percent
bismuth or less were also available but either melted at equally low temperatures,
contained hazardous elements like lead and cadmium or did not expand on solidifi-
cation. AN things considered, the procedure described herein utilized a eutectic alloy
of 58 weight percent 81 and 42 weight percent Sn[5 which does expand on solidifi-
cation just enough to retain all inside diameter deposits and features without
The process consisted of the following steps:
(A) Chips from the as-received cast slab were heated in a pyrex beaker to
about 50 F above their eutectic melting point of 281 F. Melting only
what is needed limits the introduction of undesirable, excessive amounts
of oxide dross in the casting. However, we have been able to skim the
oxide dross to facilitate many reuses. The excess 50 F provides for
good fluidity on casting.
(B) Whole tube sections from one-half to one inch long were held in a vertical
position and the mounting alloy was cast into them. Usually the support-
ing base for the tubes was a poor thermal conductor to slow the freezing
process down. Thin waled tubes from one-quarter to one inch diameter
were mounted successfully, as were thicker walled sections with these
same size holes.
(C) Samples whose outside surfaces needed careful preservation were also
easily accommodated with this alloy mounting process by surrounding the
Here’s what’s next.
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Katz, O. M. A new metallographic procedure for edge retention of enclosed surfaces, article, August 1, 1994; United States. (https://digital.library.unt.edu/ark:/67531/metadc1354521/m1/4/: accessed April 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.