The manufacturing process of blades includes forging, followed by machining, pickling, and the blades then undergo stabilised tempering after achieving its geometry. The product is then inspected through non-destructive techniques. The inspection techniques include magnetic particle inspection, zyglo and ultrasonic tests. After inspection, the material undergoes vibro-tumbling of profile, which is then followed by the root strain hardening. The blades are then plated. The plate process is typically welding process; the blades are plated with rotor through welding. The plating of the root of blades is conducted with silver plating. The plating of aerofoil is conducted through nickel-cadmium plating; the plates are then annealed through thermal diffusion. The intent of plating i.e. the material build up is to prevent fretting fatigue. The plating offers "cushion effect and lubrication, the root of the blade is plated with silver 3-6 micrometer thickness" (Bruce, 1997).
The machining process has been further advanced, and the electrical discharge machining process is commonly employed. This process is thermal process, the electrode is melted and vaporised. The process is common for the construction of the blades. ...Show more