Degradation of the gas turbine hot-gas-path components, the 1st stage blades and vanes, serviced for a period was evaluated by measuring the mechanical properties. For this, tensile and impact tests on these gas turbine parts were performed. Microstructure of the substrate and coating layers were also observed. The mechanical properties of the serviced blades were degraded by about 30% comparing with those of unused ones. In terms of the microstructure, the dissolution of the secondary g’ phase and subsequent coarsening of precipitates were observed in the substrate. And the interdiffusion zone near the coating layer was disappeared.