Applying a device to mitigate sensitization in aluminum structures will be less labor intensive than the current process. NMC photo
The Navy Metalworking Center (NMC) is leading a Navy ManTech project that is addressing the major contributor to the cracking – the sensitized microstructure in the 5456 aluminum-magnesium alloy.
Cracks in the superstructure of the CG 47 Cruiser class ships require extensive repair, i.e., removing and replacing the affected plate as well as all of the outfitting obstructing the area.
NMC and its Integrated Project Team (IPT) will develop, demonstrate, and implement a portable heat treatment system that reverses sensitization in 5456 series aluminum alloys, thereby restoring the affected material in the ship’s superstructure to a stabilized condition. Members of the IPT, consisting of the in-service Surface Combatants (PMS 400) and Littoral Combat Ship (LCS) (PMS 501) Program Offices; Naval Surface Warfare Center, Carderock Division; NAVSEA 05P2; NAVSEA 05D; NMC; ElectraWatch; and DDL Omni, will conduct tests to determine the optimal treatment time and temperatures as well as the process limits.
Reverse sensitization will give the Navy a low-cost alternative to the current crop-and-insert method. The reverse sensitization repair process can save as much as $1.7M per CG 47 ship. Thus, the implementation of this technology could result in a cost avoidance of as much as $25.5 million for 15 ships serviced within five years. The LCS program will also benefit from this improved technology, as several frames in close proximity to the exhaust plenum had to be replaced recently on LCS 2 (the USS Independence), at a conservative estimated cost of $500,000. By repairing the material in place instead of replacing the frames, the repair cost could have been halved. The upcoming block buy will raise the LCS fleet to 32 hulls within five years after award; if half of those ships experience a similar failure, the cost avoidance for the Navy would be $4 million.
The new process is expected to be implemented at Norfolk Naval Shipyard on CG 47 at the end of FY15.
Naval Surface Warfare Center, Carderock Division
PMS 501 Littoral Combat Ship Program Office