During the oxidation of Kanthal resistance wires, a thin layer of oxide forms on the surface. This layer is porous and gives no protection against further oxidation. In this study, the microstructure and growth kinetics of the oxide formation were investigated at relevant temperatures. X-ray diffraction, energy dispersive spectroscopy, and scanning electron microscopy were used to investigate the oxide layer thickness.
Field, Kevin G., and his research group were interested in the oxidation of Rene 41. They developed a radiometric emittance measurement apparatus, which measured the emittance of oxidized samples. They found that the oxidation of Rene 41 was stable at 1150 K. The oxidation rate was also monitored using a thermogravimetric technique. They found that the average drift rate was -9 microstrain/hr. However, the short-term drift rate was higher than the long-term drift rate.
Kanthal resistance wires were also studied in the presence of different substances. The aluminum content of KANTHAL alloys was reduced significantly when attacked by substances. The alloy was oxidized in the presence of nitrate, silicate, chlorine, and CO. This caused the formation of a grayish-black oxide.
The alloy was also oxidized with 50% H2O and 50% O2. This method was used for small diameter wires of high-temperature alloys. The initial temperatures of the wires were 1016, 1134, and 1354 degC. The operational temperature was lower for the wires with increasing gauges. In the non-contact configuration, the operational temperature was 186, 197, and 240 degC.