Conditions for formation of MAX phase Cr2AlC in electrospark coatings deposited onto titanium alloy

• Coatings were deposited by pulsed electrospark deposition using Cr2AlC electrode.
• The Cr2AlC content of the coatings up to 50% can be obtained by annealing at 700 °C.
• The TiC sublayer promotes the MAX-phase formation.
• Coatings show a high short-time oxidation resistance at 900–1000 °C.
• Friction coefficient of coatings is close to 0.6 at 25 °C and 0.4 at 700 °С.

The technique of low-energy pulsed electrospark deposition (PED) with Cr2AlC electrodes was used to apply a protective layer onto the surface of Ti substrate. This was done in two ways: (a) thermal treatment of as-deposited coating and (b) preliminary creation of a TiC sublayer followed by PED. Upon annealing at 700 °С for 1 h in air, the coating was found to largely consist of MAX phase Cr2AlC. A TiC sublayer preliminary сreated onto the Ti surface was found to suppress the Ti diffusion into the coating and thus to hamper the reaction of Cr2AlC with Ti. The coatings were characterized by SEM/EDS, XRD, and XPS. After thermal treatment, the coatings showed high wear resistance and friction coefficients of 0.6 and 0.4 at 25 and 700 °С, respectively.