Name two non-destructive testing techniques used for turbine blades and what defects they detect.

• A. Ultrasonic testing can only detect surface cracks.
• B. Magnetic particle testing is used for turbine blades made of non-ferrous materials.
• C. Radiography detects only interior cracks.
• D. Dye penetrant detects surface cracks; eddy current detects surface and near-surface cracks and coating delaminations.

Answer: (D)