Navy PH stainless steel hydrofoil rudder/propeller

Navy used precipitation-hardened stainless on hydrofoil rudders or propellers — high strength, lightweight, 180 ksi. Aluminum hull, PH stainless in the drive end. "We created a few problems back there" — implies a welding consulting episode not developed here.

There are precipitation-hardened stainlesses where you add copper, titanium and aluminum, and you can get precipitates with nickel titanium, nickel aluminum, or just straight copper-type precipitates in the iron. You can get 180 ksi. This is what the Navy used to use, the PH stainlesses, on their hydrofoils. They needed — I think it was the rudders. It was either the rudders or the propellers. They wanted high strength, lightweight, and they were going to PH stainlesses. Most of the hull was aluminum, but back in the drive end they were using some PH stainless. We created a few problems back there, but nonetheless.