Whether be it in airborne transportation, chemical industries, or energy production, an increase in combustion temperature helps raising system efficiency, according to thermodynamical principles like the Carnot process. High-temperature environments like those drive most of the technically relevant alloys to the point of reaching the limit of failure. Thanks to the high melting temperature of Cr-rich Chromium-Silicon alloys and their excellent mechanical strength at elevated temperatures, the use cases in mentioned high-temperature applications are numerous.
However, this kind of alloy tends to form volatile and mechanically unstable chromium oxides, that easily flake off, leaving the alloy vulnerable to nitridation beyond 1000 °C. Regarding these properties, the Cr-Si alloys must be made less susceptible by further alloying to eliminate the performance-limiting aspects.
This study examines the effect of the addition of reactive elements like Yttrium, A15-phase formers like Germanium and Molybdenum, and glass phase formers like Boron and Germanium on high-temperature oxidation resistance. Additionally, the effect of a deposited Al-diffusion coating of a thickness of around 25 µm is investigated. The examinations are carried out during cyclic oxidation testing at 1200 °C in lab air for a total of 30 h with individual heating cycles of ten times one hour, two times five hours, and one time ten hours. The oxidation and nitridation phenomena of the alloyed samples are being analyzed and compared to pure chromium, treated in parallel with the same parameters.
Whilst pure Chromium experiences a mass loss of 21 mg/cm$^2$  in total after 30 h of treatment, the addition of reactive elements halves the mass loss. Regarding an initial penetration depth of nitridation in pure Chromium of around 400 µm, penetration depths were reduced by 87 %.
Besides reactive elements, Al$_2$O$_3$ formation improved the mass loss during exposure, and so the oxidation resistance. The overall highest increase in resistance was found for the Ge-containing alloys.