The maximum operating temperature for Monel 400 nickel alloy foil is around 600°F (315°C). At this temperature, the alloy maintains its excellent corrosion resistance & mechanical properties. However, it’s important to note that Monel alloy 400 has a relatively low creep & stress rupture strength. It means that it is not recommended for use at temperatures above 600°F (315°C) for prolonged periods of time. It is also important to note that the maximum operating temperature for Monel alloy 400 may be affected by factors such as the specific conditions of the environment in which it is used, the presence of impurities or contaminants, and the rate of temperature change.