54 Applications

Ni3Al alloy IC-221M is being used in furnace furniture, steel transfer rollers, and in a number of other high-temperature applications.

Heat treaters use tables, trays, posts, fixtures, and other supports, commonly called "furnace furniture," to hold treated parts in the furnace (Figs. 5.5 and 5.6).

FIGURE 5.5 Pusher carburizing furnace trays.
FIGURE 5.6 Batch carburizing furnace trays.

Delphi Automotive Systems Corporation uses furnace furniture at its Saginaw (Michigan) Steering Gear plant to hold gears for power steering systems while hardening them in a high-temperature carbon atmosphere. At the end of this carburizing process, the gears and their supporting furniture are quenched from 900°C to room temperature. The same furniture is subjected to this cycle with every load of gears processed. This repeated thermal cycling and the carburizing atmosphere makes this a severe challenge to any furnace material. Delphi engineers are replacing chromium alloy furniture with nickel aluminide. The nickel aluminide forms a thin film of aluminum oxide on its surface, preventing carbon from diffusing into the body of the metal. HP, a chromium nickel alloy, furniture lasts 6 months. The nickel aluminide furniture is still in operation after 39 months.

The superior strength of Ni3Al permits heavier tray loading while decreasing the tray size. The use of nickel aluminide has resulted in furniture replacement savings, higher operating temperature, a 10% throughput increase, reduced cost, reduced energy use, and less waste. The efficiency gain allows Delphi to postpone plans to build a new furnace.

A major U.S. steel maker heat treats steel plates to soften them and then pass them over transfer rollers to provide a smooth surface finish and move them through the process. Due to the high process temperatures, conventional rollers sag, jostle the plates, develop oxide particles, and blister, scratching the plates. Nickel aluminide rollers withstand the heat and are three times stronger than the conventional rollers. The nickel aluminide rollers are only inspected once per year versus the conventional practice of shutting down every 6 weeks, inspecting rollers, grinding out particles, and replacing sagging rollers. The use of nickel aluminide rollers reduces downtime, the number of spare rollers and the cost of repairing rollers, resulting in savings for the plant. The rollers are centrifugally cast of nickel aluminide alloy, IC-221M, manufactured by Sandusky International Corporation, product number 184687. Cast rings were welded together at Oak Ridge National Laboratory for the initial tests. Engineers used IC-221LA filler metal provided by Stoody Company (Bowling Green, Kentucky) (See Figs. 5.7 and 5.8). Preapplication testing included weld tensile strength, fatigue (360 cycles, 871°C (1600°F) to room temperature), hardness versus time, microstructure examination, and oxidation behavior.

Nickel aluminide is also being evaluated as statically cast triunions for rollers in austenitizing and hydrogen annealing furnaces.

Ni3Al is being evaluated as thick-walled tubes and pipe because iron oxide does not stick to it. Ni3Al has less creep and better resistance to carbon and oxygen than conventional materials such as cast stainless steels (HU and HP modified).

United Defense is supplying nickel aluminide rails to Rapid Technologies Corporation (Newnan, Georgia) for its walking-beam furnaces. Its heat-treating furnace moves steel bars rapidly through a high-temperature zone. The concept requires rapid heating, resulting in less natural-gas and cooling water. Without nickel aluminide beams, these savings and their product would not be possible.

FIGURE 5.7 Furnace roll for hydrogen annealing furnace.
FIGURE 5.8 Blistering of conventional furnace roll.

Ni3 Al is being evaluated as statically cast die blocks for the hot forging process to increase life because of its yield strength at 850°C (1562°F) and its resistance to oxidation, which is better than cast stainless steels. Ni3Al is being evaluated as cast hot pressing dies for permanent magnet material. It has excellent chemical compatibility and high-temperature yield strength compared to IN-718.

Cast-shaped rods of Ni3Al are used as industrial furnace heating elements to increase life by increased oxidation resistance and sagging. They replace FeCrAl alloys.

Ni3Al powder is used as a binder for tungsten and chromium carbide as tool and die materials. It improves wear resistance and aqueous corrosion resistance in certain acid solutions. It replaces expensive cobalt currently used as the binder material.

Ni3Al is being used in circuit boards as a metallic core that absorbs more heat than a monolithic Al2O3 board. This enables the board to handle higher power devices.

Other applications include tube hangers, ethylene cracker furnace tubes, gas filters, radiant burner tubes (Fig. 5.9) (see Chapter 3 for descriptions of these four applications), glass processing equipment, furnace belt links (Fig. 5.10), container dies, binder for tool and die material, auto belt tooling, furnace heater (and other heater elements), mufflers, return bends, firing legshot forging dies, hot pressing dies, trays, mufflers, brake components (Fig. 5.11), boiler tubes, catalytic converter substrate, salt bath containers, sulfuric acid containers, mixers, and other parts in corrosive solutions.

In 1995, 50,000 lb of Ni3Al were made.

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