Alloys of the Fe-Cr-Al system possess good oxidation and heat resistance. They are used chiefly for heating elements in the electrical industry. Because of their ability to withstand oxidation, the alloys can be employed under high-temperature conditions, while their good ductility enables them to be processed into wire and strip by hot and cold working.
Fe-Cr-Al alloys intended for prolonged operation at high temperature. Fe-Cr-Al alloys are creep-resistant over a wide range of temperature, which is another of their important qualities.
Ferritic Fe–Cr–Al alloys have several potential advantages, i.e. lower raw-material cost, superior oxidation resistance, lower density, and lower thermal expansion coefficient than the Ni-base super-alloys and have found applications in a wide range of high-temperature oxidation environments such as heating furnace, nuclear reactor, petroleum refinery and automotive exhaust system. In spite of their favorable properties, however, these alloys have not yet been used above 873 K, since their mechanical properties are not satisfactory at high temperatures.
Precipitation-strengthened alloys, e.g. nickel-base super-alloys, have been extensively studied over the past decades. These alloys generally show anomalously high stress dependence and temperature dependence. Furthermore, there is a pronounced transition in the stress/creep rate relationship where the high stress dependence of the creep rate in the high stress region is replaced by a lower stress dependence.
To meet the needs for high-temperature application above 873 K, Fe–Cr–Al alloys might be strengthened by the Ni-Al-type precipitates. A number of studies have shown that the addition of 2–4 wt% Ni to Fe–19Cr–2Al alloy followed by subsequent ageing treatment leads to the precipitation of ordered coherent β′ particles, thereby significantly enhancing the mechanical strength of the alloy at room temperature. However, there appears to be no published literature on the creep behavior of such β′(Ni-Al) precipitation-strengthened ferritic Fe–Cr–Al alloy. The alloy shows a single-slope behavior in the stress/creep rate relationship and anomalously high values of the apparent stress exponent and creep activation energy.