Creep Life Assessment of Repaired Turbine Blade from Two Substances

Gas Turbines have wide applications in power plants and aerospace industries. Nowadays, based on welding of two different materials, some economic methods for repairing turbine blades have been developed. In this paper, a method, for determining creep life of a RTB (Repaired Turbine Blade) of two substances, based on transient FEM method had been developed. To find the effect of the difference between creep properties of materials of two substances RTBs, a simple 2D model under centrifugal forces was modeled. The base and filler metals were GH 4049 and Inconel 718, respectively. Creep is time dependent deformation of metals at elevated temperatures, therefore stresses are also time dependent. Hence, the life of RTB was estimated using damage fraction rule. These were performed using APDL ANSYS commercial software codes. To verification of the method, an experiment test has been established which defined the way critical elements behaved. In this experiment, pure lead was used as softer and Tin70%-lead30% was used as harder metal in creep. Experimental and numerical models were compared and good agreements between them were found. Rupture point was truly predicted and relative error was only 6% (traditional methods had 20% error). Results showed that the difference between creep properties of base and filler metals for supposed geometry and repaired location, leads to 90% decrement of designed life.