Precipitation hardening (PH) alloys
Alloys that gain strength by aging: after solution annealing, a controlled heating precipitates fine particles that pin dislocations and raise the yield strength above 1,000 MPa.
Precipitation hardening (PH) alloys: alloys supplied by Dustre
Forms: Bar, Plate, Forging and flange, Casting, Wire. Click an alloy to see standards by form, composition, properties and equivalents.
| Material | UNS | W.Nr. / EN | Forms |
|---|---|---|---|
| 15-5PH – UNS S15500 (XM-12)Precipitation-hardening stainless · Martensitic precipitation-hardening stainless steel (Cr-Ni-Cu) | S15500 | 1.4545 | Bar, Plate, Forging and flange, Casting |
| 17-7PH – UNS S17700 (Type 631)Precipitation-hardening stainless · Semi-austenitic precipitation-hardening stainless steel (Cr-Ni-Al) | S17700 | 1.4568 | Bar, Plate, Forging and flange, Wire |
| A-286 / Alloy 660Precipitation-hardening stainless · Precipitation-hardenable Fe-Ni-Cr superalloy | S66286 | 1.4980 | Bar, Plate, Forging and flange |
| 17-4PH stainless steel – UNS S17400 (ASTM A564 Type 630)Precipitation-hardening stainless · Martensitic precipitation-hardening stainless steel (Cr-Ni-Cu-Nb) | S17400 | 1.4542 | Bar, Plate, Forging and flange, Casting |
| 17-4PH round bar – ASTM A564 Type 630 / AMS 5643Precipitation-hardening stainless · Rolled or forged precipitation-hardening stainless bar, condition A or H1150 | S17400 | 1.4542 | Bar, Forging and flange |
| Maraging 250Alloy steel · Age-hardenable 18Ni(250) maraging steel | K92890 | 1.6359 | Bar, Plate, Forging and flange |
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About precipitation hardening (ph) alloys
The martensitic PH stainless grades 17-4PH and 15-5PH, hardened by copper, are the most used: pump shafts, valve stems, gears and aerospace parts, with corrosion resistance close to 304. 17-7PH is semi-austenitic and serves springs and thin parts. A-286 (Alloy 660) is an iron-nickel superalloy hardened by titanium and aluminum, used in fasteners and turbine components up to about 700 °C. Maraging steels (18 % Ni with cobalt and molybdenum) reach 1,700–2,000 MPa with low carbon and good toughness. Age-hardenable nickel alloys (Inconel 718, X-750, Monel K-500) are in the nickel alloys group.
The aging condition sets the balance of strength and toughness: H900 gives the highest hardness; H1025 and H1150 trade strength for toughness and stress corrosion resistance. For H₂S service, NACE MR0175 / ISO 15156 accepts 17-4PH only double aged (H1150D) and with a maximum hardness of 33 HRC.
See also
Frequently asked questions
What does H1025 mean for 17-4PH?
It is the aging condition: H means treatment from the solution annealed condition (A) and 1025 is the temperature in °F, about 552 °C. The higher the number, the lower the hardness and the higher the toughness.
17-4PH or 15-5PH?
The composition is similar, but 15-5PH has less chromium and is practically free of delta ferrite, which gives better transverse toughness in large sections. That is why it is preferred for forged aerospace parts.
