PROBLEM / OBJECTIVE
The objective of this project was to develop and implement joining processes that improve performance, reduce costs and repair time for nickel aluminum bronze propellers. The need for this project is driven by the high cost of in-service repairs of ship and submarine propellers. Current practice is to repair defects and rebuild surfaces by arc welding; and then, straighten where necessary to restore the correct geometry. Some of the most recent designs make propeller removal extremely difficult and costly. Improved repair methods are needed to reduce repair time, increase the strength of local areas, and extend the life of propellers.
ACCOMPLISHMENTS / PAYOFF
Friction stir processing (FSP) is a solid‑state process that can be used to repair surface and near surface defects, and increase material strength. During this project, FSP was combined with a robot to provide a portable repair method for in-service propellers. In addition, pulsed gas metal arc welding (GMAW-P) procedures were developed and implemented to permit high-productivity, out-of-position arc welding of those propellers that cannot easily be removed from the vessel.
Implementation and Technology Transfer:
This project supports the future implementation of friction stir processing for repair of propellers. FSP parameters were developed and qualified to Navy requirements on both cast and arc welded nickel aluminum bronze materials. GMAW-P procedures were developed to permit out-of-position welding of Virginia Class propellers. The GMAW-P technology was implemented at the Naval Foundry and Propeller Center (NFPC), where welders were trained and the procedures qualified to Navy requirements.
Expected Benefits and Warfighter Impact:
Fiction stir processing can reduce the repair time for surface and subsurface defects in propellers. The process also can strengthen critical areas as well as reduce residual stresses and distortion. Pulsed gas metal arc welding of Virginia Class propellers permits in-situ repair of major defects with a five-fold improvement in productivity compared to current practice. This will reduce dry dock time required to remove propellers and generate an estimated annual savings of $200K.
Navy ManTech Investment: $1.113M
Naval Surface Warfare Center, Carderock Division
Naval Foundry and Propeller Center
Friction Stir Link
To learn more, contact Harvey Castner, Senior Project Manager, at 614.688.5063 or email@example.com.