ALLOYS
> NICKEL ALUMINIDE
 Intermetallics are a relatively new category of material,
unique in that intermetallic materials exhibit characteristics
of both metals and ceramics. Due to the unique combination
of ceramic and metallic characteristics, intermetallics have
typically shown excellent high temperature strength and very
good resistance to oxidation.
Nickel Aluminides
Ni3Al Rolls
One version of an intermetallic material that has become
commercialized is the Nickel Aluminum alloy (Ni3Al). Nickel
aluminides were developed and patented by Oak Ridge National
Laboratory (ORNL) in Tennessee, through funding from the
U.S. Department of Energy (DOE). This material has been
tested in a variety of cast parts, from furnace fixtures
and trays, to radiant tubes and assemblies, to plate hardening
furnace rolls. The oxidation resistance and resistance
to high-temperature creep have worked well to increase
the life of these parts in service life.
Nickel Aluminide alloys, in the form of Ni3Al, are a new
class of intermetallics that offer improved high-temperature
performance over traditional stainless steels and many nickel-based
super alloys. Alloy IC-221M alloy is a version of Nickel-Aluminide
which is more highly alloyed with chromium, zirconium and
molybdenum for improved high temperature ductility and improved
high temperature strength. Alloy IC-221M is an Ni3Al alloy
patented by Oak Ridge National Laboratory and is licensed
by Duraloy to produce furnace rolls in this material, utilizing
the Exo-Melt melting technology, developed by ORNL for this
material.
Two key properties of the IC-221M alloy are that the load-carrying
ability actually increases as the service temperature increases
(up to 1470o F), and exhibits a much less pronounced decrease
in strength at above 1470o F when compared to traditional
heat resistant alloys HK and HP. These characteristics make
the alloy an excellent choice for load-carrying rolls in
heat treating furnaces.
Cost Savings for Furnace Operators
Large cost savings, in both energy and productivity, can
be achieved by furnace operators through the use of IC-221M
alloy for furnace rolls. Efficiencies can be achieved through:
- not having to shut down austenitizing furnaces for
frequent regrinding of rolls to remove blisters.
- not having
to shut down and replace rolls as frequently as with traditional
HK and HP rolls.
- less rework costs on heat treated product
due to scarring on surfaces due to blisters on the roll
surfaces.
- increased yields and throughput
Case Study
In December of 2002, 101 Ni3Al furnace rolls were installed
at the former Bethlehem Steel plant (now Mittal Steel) in
Burns Harbor, IN. under a DOE-ITP funded project. All of
these rolls continue to operate after 4+ years of service,
without surface failure. Based upon current performance,
it is anticipated that the rolls will last 7 - 10 years before
shutdowns for refurbishment are needed versus 2 - 3 years
required by conventional rolls.
In the 5+ years that these rolls have been running, it is
estimated that the savings at Burns Harbor are about $1.38
million (USD) per year, primarily as a result of the elimination
of shutdowns for roll maintenance. The installation of the
rolls has demonstrated a 31.4 billion Btu/year of savings
in natural gas at the Burns Harbor facility (based upon 100,000
ton/year). Burns Harbor has also realized a 2% increase in
heat treat yields during the time these rolls have been installed.
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