The life of a heating element is basically depends on the temperature limit, environment and width of material like nichrome wire or strip. If you use large wire diameter and thicker strip, it will much timer to get oxidized so the life of the element is elongated. Basically the resistance heating wire producers prefer to use 3mm diameter of heating wire strip of width 2mm in the industrial heating operations.
Second essential factor that influences the life of heating elements is kind of services taken from them that is nonstop or periodic. The continuous heating and cooling cycles produce thermal stress in the heating alloy that destructs the sheath of surface oxide of the element and exposes the metal in the open environment. The open non – oxidized alloy gets oxidized rapidly that decreases the life of material. The spalling of nichrome alloy’s oxides can pollute the product whereas the oxidation of Fe – Cr – Al is more reliable and opposes the spalling. The temperature’s impact on the life of the different elements like nichrome resistance wire and iron, chromium and aluminum alloys is variable.
The Maximum furnace temperature is 1200 °C and the reference point is iron, chromium and aluminum alloy. If we analyze the alloy economy deeply it demonstrates that the initial cost of iron, chromium and aluminum alloy is lower as compare to nichrome alloy for the same purpose. The nichrome heating wire has larger life cycle charge, that’s why the iron-chromium-aluminum alloys are primarily used to replace the nichrome alloys in the particular applications.
Other kind of heating elements are silicon carbide elements; these are available in the extensive series of sizes and shapes. These are self helper that enables them to be utilized in the furnace applications that are made on the wider scale and for long time span. The silicon carbide elements are capable to perform in the elevated temperatures and higher watt loadings than the metallic alloys and these are relatively convenient to transform in the hot temperature of furnace.
The drawbacks of silicon carbide is that these are more expensive power management equipments than the nichrome heating wire and their electric resistance increases with the passage of time, so these need more maintenance as compare to nichrome alloys or molybdenum disilicide compounds. Also the silicon carbide is a kind of ceramic material, so there is a risk of rupture.
The producers of silicon carbide basically design a group of elements by using the different classes of materials and by following the various production methods to design each product for particular operation. As the lower MET value tends to cause operation in the vacuum due to damage of tough vacuum by silicon dioxide layer produced in the pre oxidation and also silicon carbide vaporizes at the higher temperature in the large vacuum environments.
The entire silicon carbide elements get oxidized and increase the resistance while these are in operation. Therefore they are no longer referred as heating elements and replaced by nichrome resistance wire to fulfill the particular heating operation needs.
Isha Changotra has wide experience in metals industry and is working for a renowned super alloys manufacturer located in China and United States. With extensive insight in metals and high performance super alloys, she aims to provide most useful information for folks engaged under this niche.
Metals, Alloys-Information Guide 
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