Abstract: A method and apparatus for producing turbine blade roots (23) utilize an electro-discharge machining apparatus (10) to machine critical portions of the blade root (23) and a peening apparatus (25) for peening of the machined portions. The electro-discharge machining of the blade root leaves recast layers (22) on the surface of the blade root (23), and high residual tensile stresses are found in the surface of the blade root (23), which could lead to crack propagation. Peening of the machined surfaces leaves compressive residual stresses near the surface and reduces the recast layers (22). The resulting blade root (23) meets the same specifications for durability and tolerances as a blade root machined using the conventional transfer line type cutting process, but at a fraction of the cost.

Abstract: The advantageous light-technical properties of the alkaline earth and rare earth halides can be utilized without an excessive thermal load of the wall of the vessel occurring, if the discharge vessel contains at least one halide of iron, of cobalt or of nickel as a compound-forming metal halide.