Advanced Metalworking Solutions for
Naval Systems that Go in Harm's Way

Development of 15-5PH Forgings for Torpedo Muzzle Door Lever Arms

Implementing 15-5PH forgings for critical components of Navy submarines will improve mechanical properties, reduce material costs and eliminate periodic replacement of components. Corry Forge Company photo


This project sought to substitute the K-Monel forgings with modified 15-5PH steel which provides improved mechanical properties and corrosion resistance, negating the need to replace components during the submarine’s lifetime.


The torpedo tube muzzle door operating linkage for the Los Angeles Class submarine (SSN 688) and subsequent classes of Navy submarines include several critical components produced from K-Monel® (Ni-Cu-Al) forgings. The components do not function as needed in a corrosive seawater environment and must be replaced after eight years of service.

Technical Approach

This project developed critical forging and heat treating parameters that will result in material properties tailored for this specific application. 15-5PH steel was evaluated for use on Los Angeles, Ohio, and Seawolf classes of submarines, as well in VIRGINIA Class submarine construction.


By eliminating the need to periodically replace these critical components in the in-service fleet, the Navy has estimated the cost savings to be approximately $9.4M over the remaining life of these 70 hulls. Material cost savings will also result from replacing K-Monel with 15-5PH forging s in approximately 292 tube linkage assemblies on 70 submarines representing four different classes. 15-5PH steel offers property improvements over K-Monel, including approximately 20-30 ksi yield strength and improved corrosion performance in this application.


Retrofit of existing K-Monel linkage components on the Los Angeles, Ohio, and Seawolf classes of submarines will begin in FY14 after sufficient quantities of machined components are available. The project results were not implemented on VCS at the time of the project’s completion.