RA 602 CA - Rolled Alloys

Grain Growth
The brittle fracture of components exposed to
extreme temperatures is a common occurrence.
At temperatures near or exceeding the annealing
temperature of a heat resistant alloy, grain growth is
likely to occur. Extensive grain growth can result in a
loss of ductility. As a result, the component can be
prone to brittle fracture. An alloy 601 corrugated muffle
that suffered brittle fracture due to combination of
extensive grain growth and carburization is shown
above.
The results of testing at 2050°F (1121°C) are detailed
in the table below. The information provides a
comparison of various heat resisting alloys that are
commonly used above 1900°F (1038°C). The data was
compiled from intermittent exposure of sample
coupons to 2050°F (1121°C) for a total of 990 hours.
Each sample was in the mill annealed condition. The
figure at right shows a sample of RA 602 CA after long
term exposure to 2100°F (1149°C).
3
RA 602 CA
Brittle fracture of an alloy 601 muffle from the combination of extensive grain growth and carburization.
Sample of RA 602 CA examined after exposure to
2100°F (1149°C) for over 3150 hours. The grain size
was originally ASTM 7. After the 3000 hour test
period the grains had only grown to ASTM 5.5.
Magnification: 90x
Effects of High Temperature Exposure on ASTM Grain Size8 - 2050°F (1121°C)
Time ASTM Average Grain Size
Hours RA 602 CA RA601 601GC RA330 RA 353 MA RA333 RA600
0 7 5 5.5 7 6 4 8
2 7 5 5.5 3.5 4 4 4
24 7 1.5 5 3.5 3 3.5 1
72 7 1 5 3 2.5 3 0
184 6.5 1 3.5 3 2.5 2.5 0
344 6.5 0 3.5 2.5 2 2 0
510 6.5 0 3 2 2 2 00
670 6.5 00 3 2 1.5 2 00
830 6.5 00 3 2 1.5 2 00
990 6.5 00 2.5 1.5 1.5 1 00