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corrodant under isothermal conditions.
Inconel and types 316, 347, and 446
stainless steels have been tested in
this apparatus. Greater attack than
that obtained in ordinary static cor-
rosion tests was noted onall materials
tested. It should be emphasized that,
except in the test of the type 347
stainless steel specimens, these were
actually three-component tests because
the spinner pot was fabricated of type
347 stainless steel.
The effect of this test on Inconel
spun at 400 ft/min for 72 hr at 816°C
is shown in Fig. 11.8. A 0.5-mil
surface layer, with 0.5 m i l of inter-
granular voids beneath it, is apparent.
This surface layer may be a mass
transfer effect caused by t,he three-
component system used during test.
The analysis of a portion of the
surface layer scraped from the specimen
showed 64% nickel, 27.5% chromium. and
PERIOD ENDING DECEUBER 10, 1952
8.3% iron. (The composition of Inconel
is 80% nickel, 15% chromium, and 5%
iron. 1
The intergranular attack on type
316 stainless steel is shown in Fig.
11.9. This attack extended to a depth
of 1 to 2 m i l s near the front, or
leading edge, of the tubular specimen
and, as would he expected, was less
severe at the trailing edge, where the
depth of attack was 0.5 to 1 m il. The
test was conducted at 816°C for 100 hr
with a speed of 400 ft/min. Type 347
stain 1 ess s tee 1 suffered intergranular
attack to 2 m i l s after testing for 74
hr at 816°C with a speed of 400 ft/min.
After 53 hr at 816°C at a speed of
400 ft/rnin, type 446 stainless steel
showed slight intergranular attack to
a depth of less than 0.5 m i l . The
results of these tests are summarized
in Table 11.10.
SURFACE LAYER
ATTACHED REGION
INCONEL
Fig. 11.8. Inconel from Spinner Test with Sodium at 816OC for 72 hr at a
Speed of 400 ft/ein. 500X.
145