A new MAX phases-based electroconductive coating for high-temperature oxidizing environment

In the paper, results of variations of structure, oxidation resistance, and electrical conductivity of novel MAX-phase composite coating are presented. The characteristics of highly dense Ti-Al-C composite bulks and vacuum-arc deposited 6 μm thick coatings before and after heating at 600 °C in air for 1000 h were compared. High electrical conductivity (σ = 1.3·106 S/m) of the highly resistant toward oxidation (Δm/S = 0.07 mg/cm2) Ti-Al-C coating was preserved after long-term heating in air. It was found that the specimen surface layers of MAX-phases Ti3AlC2 and Ti2AlC based bulks and chromium-containing Crofer 22APU steel became semiconductors because of high-temperature long-term oxidation (at 600 °C). The vacuum-arc deposited Ti-Al-C composite coating revealed high oxidation resistance and electrical conductivity along with good mechanical characteristics, namely nanohardness H(10mN) = 9.5 ± 1.5 GPa, and Young’s modulus E = 190 ± 10 GPa, which make it very promising for interconnects of solid oxide fuel cells (SOFCs).