15-5PH Stainless Steel (UNS S15500): Aerospace & High-Strength Applications

AMS 5659 / ASTM A564 · Published: 2026-06-01 · Updated: 2026-06-02

15-5PH is a martensitic precipitation-hardening stainless steel produced by vacuum arc remelting (VAR) or electroslag remelting (ESR). Its chemical composition is identical to 17-4PH except for slightly higher nickel (3.5-5.5% vs 3.0-5.0%) and more tightly controlled chromium (14.0-15.5% vs 15.0-17.5%). The VAR/ESR production route yields significantly cleaner steel with lower inclusion content, translating to superior transverse ductility and impact toughness — the key advantage over conventionally melted 17-4PH. Transverse reduction of area for 15-5PH H1025 is typically >45% vs >35% for 17-4PH.

Primary applications: aerospace structural components (landing gear parts, actuator fittings, helicopter rotor components) where transverse properties are critical and failure is not an option. Also specified for nuclear reactor components (control rod drive mechanisms) where material consistency and traceability are paramount. The cost premium for 15-5PH over 17-4PH is typically 20-40% due to the VAR/ESR processing. When to pay this premium: applications where the part is loaded in the transverse direction (short-transverse properties matter), or where inclusion-initiated fatigue failures could be catastrophic. For axially loaded shafts where the principal stress aligns with the longitudinal direction, 17-4PH is adequate.

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