Improving the oxidation resistance of Inconel 718 high-temperature nickel alloy using combined surface engineering technology

To increase the oxidation resistance of the Inconel 718 Ni alloy, a hybrid technology is proposed that combines electro-spark alloying (ESA) and magnetron sputtering (MS). Multiphase ZrSiB (ESA), ZrSiB, MoSiB, and CrAlSiB (MS) electrodes were obtained by self-propagating high-temperature synthesis. The study of the structure, composition and properties of single- and double-layers has been carried out. ZrB2 (73 wt.%), Si (21 wt.%), Ni and NiSix traces (<5 wt.%) were detected in the ESA-layer. The ESA-layer had a hardness of 19 GPa and elastic modulus of 351 GPa. The ZrSiB MS-layer contained a h-ZrB2 phase with a 4 -17 nm crystallites and Si-based amorphous regions. The layer hardness and elastic modulus were equal to 22 and 256 GPa, respectively. The MoSiB MS-layer had a conical structure, contained the h-MoSi2 and B-based amorphous phases. The layer showed hardness of 27 GPa and elastic modulus of 389 GPa. The Cr2Al, CrBx, and CrSi2 phases were found in the CrAlSiB MS-layer with hardness of 19 GPa and elastic modulus of 260 GPa. The 4.8 mu m oxide film was formed on the surface of the Ni alloy after annealing in air at 900 degrees C. The depth of the oxidation for ZrSiB/ZrSiB, MoSiB/ZrSiB, and CrAlSiB/ZrSiB MS-ESA coatings was 9.2, 0.4, and 0.12 mu m, correspondingly. The ESA-layer acts as barrier to reduce the diffusion of elements from the substrate. Two-layer MoSiB/ZrSiB and CrAlSiB/ZrSiB coatings increase the oxidation resistance of the Ni alloy by 12 and 40 times, respectively, and can be recommended for deposition onto aircraft engine parts.