The necessity of evaluation of working capacity of parts of aircraft gas turbine engines (GTE) promotes application of methods of numerical prediction of tendency to crack formation, registration of indices of line heat input in the product in surfacing process, development and testing of special procedures for determination of high-temperature mechanical characteristics of samples from various zones of welded joint ‘base–deposited metal’. Numerical prediction of a kinetics of temperature and stress-strain states during deposition of plate edge taking into account dependent on temperature thermophysical ($c_\gamma$, $\lambda$, $\alpha$) and mechanical ($E$, $\sigma_u$) properties of material is carried out based on the algorithms developed at E. O. Paton Electric Welding Institute. As determined, for ZhS6K alloy the rise of deposition height to $\cong$ 12 mm and its length for more than 100 mm rapidly increases the possibility of crack appearance in HAZ of ‘base metal–deposited metal’ welded joint and in low beads of multi-layer deposited metal. These calculations have good correlation with the data of analysis of technological probes of ZhS6–ZhS6K(NM), ZhS6–ZhS6U(NM) systems with registration of line heat input into the product. As established, the value of yield strength $\sigma_{0.2}$ for ZhS6K base metal is 1.05–1.22 and value of tensile strength $\sigma_t$ is 0.72 from corresponding indices of base metal in ZhS6K deposited metal in as-deposited state during testing at 1000°C. At the same time deposited metal has low ductility ($\delta$ = 0.15–0.65%). Investigation of microstructure and fracture surface of examined samples allowed classifying failure of deposited metal at 1000°C as an index of interval of ductility dip that take place at temperature of (0.6–0.8)$T_S$. It is recommended, that thermal treatments during restoration of turbine blades of aircraft engines shall include isothermal holding of deposited metal ZhS6K at homogenization temperature that allows rising the value of its ultimate strength to the level not lower than 0.8 in comparison with the corresponding table data of base metal and increase it to ductility values 5.8–7.2%. Thus, a complex approach to application of methods of numerical prediction of tendency to crack formation, registration of indices of line heat input into the product during deposition and analysis of the results of high-temperature mechanical tests from different zones of ‘base–deposited metal’ welded joint in perspective will allow improvement of technology for restoration of parts of aircraft GTE from difficult-to-weld nickel-based high-temperature alloys and expand assortment of parts, that can be restored using multi-layer surfacing or produce by additive technologies.