The Precipitation Hardening Stainless Steels are iron-nickel-chromium alloys containing one or more precipitation hardening elements such as aluminum, titanium, copper, niobium, and molybdenum. They develop their high strength and hardness through a variety of heat treatments resulting in a very high strength-to-weight ratio.
Semi-austenitic grades are 17-7PH and PH15-7 Mo. They are austenitic in the annealed state, and martensitic in the hardened condition. Martensitic grades include 17-4PH and 15-5PH. The PH grades achieve high tensile properties in heat treated conditions. Applications for PH steels include aerospace components, flat springs, and retaining rings.