INCONEL® alloy 740 is a nickel-chromium-cobalt alloy developed by Special Metals Corporation. The alloy is age hardenable by the precipitation of a gamma prime second phase. Potential applications include advanced power production boiler tubes and diesel engine exhaust valves.

It is nickel-base and solid solution strengthened by its content of cobalt. It exhibits excellent resistance to high temperature corrosion due to the effects of chromium. During heat treatment, niobium, aluminum, and titanium form the gamma prime precipitates required for strengthening.

INCONEL alloy 740 exhibits high strength at elevated temperatures.

Alloy 740 offers excellent resistance to corrosive attack at elevated temperature. By virtue of its high content of chromium, the alloy resists oxidation, carburization, and sulfidation. With its high content of nickel and low level of iron, alloy 740 resists high temperature attack by halides as well.

Resistance to coal ash corrosion is a requirement of service in high temperature coal-fired boilers.

Alloy 740 is readily fabricated in the annealed condition. Joining is accomplished with the gas tungsten-arc welding (GTAW) process using NIMONIC ® Filler Metal 263. If a high joint strength is required , the deposited weldment may be precipitation hardened.

INCONEL alloy 740 is still under development. While the composition is defined, work is continuing on processing the alloy.