Heat Treating of Superalloys,Heat Treating of Superalloys,Heat Treating of SuperalloysSUPERALLOYS are heat-resistant alloys based on nickel, iron-nickel, and cobalt-nickel that exhibit a good combination
of mechanical strength and resistance to surface degradation. Compositions of wrought and cast superalloys are listed in
Tables 1 and 2, respectively. The high-temperature strength of all superalloys is based on the principle of a stable facecentered
cubic (fcc) matrix combined with either precipitation strengthening and/or solid-solution hardening. In agehardenable
nickel-base alloys the γ' intermetallic (Ni3Al, Ti) is generally present for strengthening, while the nonhardenable
nickel-, cobalt-, and iron-base alloys rely on solid-solution strengthening of the fcc (γ) matrix. Iron-base and
nickel-iron superalloys may also develop, in addition to γ', second-phase strengthening from the γ'' (Ni3Nb) intermetallic
and perhaps η(Ni3Ti). Cobalt-base superalloys may develop some precipitation strengthening from carbides (Cr7C3,
M23C6), but no intermetallic-phase strengthening equal to the γ' strengthening in nickel-base alloys has been discovered in
cobalt-base superalloys.
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