Diffusion Bonded Ti-6Al-4V Helicopter Rotor Hub And Blade Spar Technology

Sikorsky Aircraft and the U. S. Army Materials and Mechanics Research Center are presently conducting two diffusion bonded manufacturing methods and technology programs to fabricate fatigue critical titanium components at low overall cost. These programs include Forge-Diffusion Bonding of large titanium - 6Al-4V helicopter main rotor hubs and Continuous Seam Diffusion Bonding (CSDB) of Ti-6Al-4V main rotor blade spars. The technical approach for reducing these concepts into practice consisted in evaluation of small scale specimens of the two processes, to obtain optimum processing conditions, and in subsequent fabrication of a large risk reduction component. The selected optimum condition for each program was incorporated into the fabrication of a risk reduction component. The component for the Forge-Diffusion Bond program was a single hub arm segment from the H53 elastomeric main rotor hub. The arm segment was fabricated, evaluated, and the bond was found to exhibit mechanical properties equivalent to parent metal values. The risk reduction component for the Continuous Seam Diffusion Bonding involved fabrication of two 10-foot spar sections which were fatigue tested and found to exhibit strength characteristics as good as or greater than present fusion welded main rotor blade spar sections.