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I bought recently 10 meters of Kanthal A1 AWG18 wire, which is a type of heating element (FeCrAl alloy). I intend to make a coil out of it, but it's no use doing that right now, I need more of it for my project (electric furnace), have ordered more of it online and am waiting a couple weeks till it arrives.

My question is this, if I use the heating element a few times in a different project (assume here that the wattage is the maximum possible), in a way that I won't twist or wind it in any way, will this affect the physical properties of the wire in ways that might make it harder for me to turn it into a coil later on, for my initial project? (I'll be winding the coil manually, it will be between 5 and 10 mm of diameter)

I ask that because heating elements tend to get more brittle with time, but I don't know how long it might take for such changes to happen.

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I have not used Kanthal, but I imagine it has similar properties to nicrome. Basically when you heat the wire up and cool it quickly, it quenches the wire. To reverse this process (or avoid it all together) you need to bring the metal to a specific temperature (without looking it up, red hot is plenty), hold it there for some amount of time, then slowly cool the wire by decreasing current to it over time. This is called annealing. The amount of time depends on the metal, but you can repeat the process again and again until you get the right amount of time. The annealing time may be something unrealistic for diy operation, and may not give you exactly the same properties you started with. But knowing this relationship and cooling the wire down slower will help.

Kanthal is rated for high temperature operation, but if you approach or exceed the rated temperature of the alloy, oxidation may occur which will progressively damage the material. In this case the damage would not be reversible. I'm not a chemist or metallurgist, but heating the material in the presence of carbon and other materials can result in chemical reactions that will modify the alloy (usually deteriorating its favorable properties).

The color of the wire during operation can give you an idea of its operating temperature, see the wiki incandescence chart below:
enter image description here

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Kanthal and nichrome/ chromel are rather different; iron base vs nickel base. Neither has a "martensite" transformation so can not be hardened by fast cooling. Little change would occur on use , possibly grain growth at high temperatures could cause limited embrittlement. You could maximize ductility by annealing: Anneal by heating to red or orange heat and quench into water.

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    $\begingroup$ I cheated and looked in a book. Kanthal does become brittle with "use" , but it was not defined. You should minimize the amount of deformation for your temporary use so not much deformation will be necessary for the final application. A quench anneal should help. $\endgroup$
    – blacksmith37
    Commented Oct 31, 2017 at 18:03

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