The Qualification of ATI 425 ® Alloy Titanium for Boeing CH-47 Chinook Helicopter Rotor Blade Erosion Caps

Erosion resistance is an important requirement in many aerospace applications, particularly for rotorcraft operating in desert environments.  The leading edge of a helicopter rotor blade has a rotational tip speed of approximately 500mph and operates in harsh environments containing dust, sand and water particles.  The Boeing CH-47 Chinook composite rotor blade leading edge structure is protected by metallic erosion caps, including a titanium nose cap over a relatively large coverage area, whose size, engineering and performance requirements dictate a controlled material and manufacturing process. ATI 425® Alloy titanium has been evaluated and qualified as an alternative material to the current Ti 6Al-4V CH-47 Chinook rotor blade erosion nose cap.  An overview of this qualification program with a formed trial part is provided.  Testing discussed includes static tensile, axial fatigue, erosion, bonding, hydrogen pickup, corrosion, and paint adhesion.  The results of a destructively tested titanium cap test article are also discussed, and the performance and manufacturability of ATI 425® Alloy are highlighted.