17-4 PH is a chromium-nickel-copper precipitation-hardening stainless steel designed to combine high mechanical strength with good toughness and corrosion resistance. Its martensitic structure can be strengthened through controlled precipitation-hardening heat treatments.

Copper plays an important role in the age-hardening response, while niobium contributes to strengthening and metallurgical stability. The alloy can achieve different combinations of strength, hardness and toughness through various aging conditions.

Common heat-treatment conditions include H900, H925, H1025, H1075, H1100 and H1150. H900 generally provides higher strength and hardness, while higher-temperature aging conditions provide increased ductility and toughness with reduced strength.

17-4 PH is widely used for shafts, fasteners, valve components, pump parts, aerospace components and other highly loaded parts where a combination of mechanical strength and corrosion resistance is required.