Inconel 600.pdf

MMPDS-01
31 January 2003
6.2 IRON-CHROMIUM-NICKEL-BASE ALLOYS
6.2.0 GENERAL COMMENTS — The alloys in this group, in terms of cost and in maximum service
temperature, generally fall between the austenitic stainless steels and the nickel- and cobalt-base alloys. They
are used in airframes, principally, in the temperature range 1000 to 1200EF, in those applications in which
the stainless steels are inadequate and service requirements do not justify the use of the more costly nickel
or cobalt alloys.
6.2.0.1 Metallurgical Considerations
Composition — The complex-base alloys comprising this group range from those in which iron is
considered the base element to those which border on the nickel-base alloys. All of them contain sufficient
alloying elements to place them in the “Superalloy” category, yet contain enough iron to reduce their cost
considerably.
Chromium, in amounts ranging from 10 to 20 percent or higher, primarily increases oxidation
resistance and contributes to strengthening of these alloys. Nickel and cobalt strengthen and toughen these
materials. Molybdenum, tungsten, and columbium contribute to hardness and strength, particularly at
elevated temperatures. Titanium and aluminum are added to provide age-hardening.
Heat Treatment — The complex-base alloys are heat treated with conventional equipment and fixtures
such as would be used for austenitic stainless steels. Since these alloys are susceptible to carburization
during heat treatment, it is good practice to remove all grease, oil, cutting, lubricant, etc., from the surface
before heating. A low-sulfur and neutral or slightly oxidizing furnace atmosphere is recommended for
heating.
6.2.0.2 Manufacturing Considerations — The iron-chromium-nickel-base alloys closely
resemble the austenitic stainless steels insofar as forging, cold forming, machining, welding, and brazing are
concerned. Their higher strength may require the use of heavier forging or forming equipment, and
machining is somewhat more difficult than for the stainless steels. Pertinent comments are included under
the individual alloys.
6.2.1 A-286
6.2.1.0 Comments and Properties — A-286 is a precipitation-hardening iron-base alloy
designed for parts requiring high strength up to 1300EF and oxidation resistance up to 1500EF. It is used in
jet engines and gas turbines for parts such as turbine buckets, bolts, and discs, and sheet metal assemblies.
A-286 is available in the usual mill forms.
A-286 is somewhat harder to hot or cold work than the austenitic stainless steels. Its forging range
is 2150 to 1800EF; when finishing below 1800EF, light reductions (under 15 percent) must be avoided to
prevent grain coarsening during subsequent heat treatment. A-286 is readily machined in the partially or fully
aged condition but is soft and “gummy” in the solution-treated condition. A-286 should be welded in the
solution-treated condition. Fusion welding is difficult for large section sizes and moderately difficult for
small cross sections and sheet. Cracking may be encountered in the welding of heavy sections or parts under
high restraint. A dimensional contraction of 0.0008 inch per inch is experienced during aging. Oxidation
resistance of A-286 is equivalent to that of Type 310 stainless steel up to 1800EF.
Some material specifications for A-286 alloy are presented in Table 6.2.1.0(a). Room-temperature
mechanical and physical properties are shown in Table 6.2.1.0(b). The effect of temperature on physical
properties is shown in Figure 6.2.1.0.
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