Method and Apparatus for Producing Turbine Blade Roots

Author:  Cox et al.
Source:  US Patent 4,888,863
Doc ID:  1988091
Year of Publication:  1988
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.