New promising challenges for the development of modern mechanical engineering are opened up by the development of highly wear-resistant and electrically conductive coatings that can ensure long-term performance of bearings and sliding mechanisms in fritting corrosion modes at temperatures of 500 ° C and above, for example, in the aircraft industry, as well as for hydrogen energetic, for example, as interconnects of solid oxygen fuel cells (SOFC).
The study of wear of 6-13 μm thick vacuum-arc deposited on martensitic heat resistant steel coatings of Ti-Al-C-MAX- phases-based showed significantly less wear compared to the sample without coating. At the initial stage, the coefficient of friction µ increased to the same value for both samples with and without coating (µ = 0.42), however, it continued to increase over time for the uncoated sample, while it was stable for the coated sample. A significant difference was observed in the profiles of the friction tracks: in the sample with this coating, the depth of the track is h~3 μm and it is quite uniform, while in the sample without the coating it is h~7 μm and local potholes are observed. The specific wear rate parameter, W, turned out to be almost 2 times higher for samples without coating (W=2.35×10^-3 mm³/N×m) than for samples with this coating (W=1.27×10^-3 mm³/N×m). The study of fretting-fatigue resistance of the coated with MAX (11.4 - 13.3 μm thick) samples using a modernized rigid cyclic bending loading machine showed that at room temperature the resistance to failure of the best coated sample was 5 times higher than without coating: the best sample with coating withstood 324,000 load cycles, and without coating only 67,000 cycles. What make promising the developed coatings for sliding bearings and mechanisms.
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 (s=1.3·10⁶ S/m) of the highly resistant toward oxidation (m/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 (10 mN)= 9.5±1.5 GPa, and Young’s modulus E=190±10 GPa and high stability in hydrogen atmosphere make it very promising for interconnects of solid oxide fuel cells (SOFCs).