Appeal No. 2002-2142 Page 2
Application No. 09/276,858
THE CLAIMED SUBJECT MATTER
The claims are directed to a method of making nickel-based superalloy single crystal
castings with a particular amount of carbon content. According to Appellants, increasing the
carbon content beyond a specified alloy carbon level reduces the formation of surface scale on
the cast superalloy and also reduces the formation of recrystallized grains after heat treatment
(specification at 3, ll. 10-19). Claims 1, 5, and 9 are illustrative of the subject matter on appeal:
1. A method of reducing as-cast metallic surface scale formed on a single crystal
casting made by solidifying a molten nickel base superalloy that includes Cr, Co,
Mo, W, Ta, and Al, comprising
providing said nickel base superalloy with a C concentration high enough
to substantially reduce formation of said as-cast metallic surface scale during
solidification, and
solidifying said molten nickel base superalloy in a mold to form said
single crystal casting.
5. A method of reducing as-cast metallic surface scale formed on a single crystal
casting made by solidifying a molten nickel base superalloy consisting essentially
of, in weight %, about 6% to 6.8% Cr, about 8% to 10% Co, about 0.5% to 0. 7%
Mo, about 5.0% to 6.6% W, about 6.3% to 7% Ta, about 5.4% to 5.8% Al, about
0.6% to 1.2% Ti, about 0.05% to 0.3% Hf, up to about 100 ppm by weight B, up
to 50 ppm by weight Mg, and balance essentially Ni, comprising
providing said nickel base superalloy with a C concentration greater than
0.04 weight % effective to substantially reduce formation of said as-cast metallic
surface scale when the superalloy is solidified as a single crystal casting, and
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