15-5 PH Stainless Steel

metal

martensitic precipitation-hardened stainless steel

15Cr-5NiUNS S15500XM-12AMS 5659Condition H900PH 15-5AISI 632

Density

7.78 g/cm³

YS (LPBF as-built (XY))

820–1030 MPa

UTS (LPBF as-built (XY))

950–1180 MPa

Elongation (LPBF as-built (XY))

12.0–26.0 %

Elastic modulus

190–205 GPa

Thermal conductivity

13.0–15.2 W/m·K

Composition — UNS S15500 / ASTM A693 / AMS 5659

Element	Min %	Max %	Notes
Fe	bal.		balance
Cr	14.00	15.500	Lower Cr vs. 17-4 PH (15.5–17.5%) — primary corrosion resistance via Cr₂O₃ passivation
Ni	3.50	5.500	Austenite stabiliser; similar to 17-4 PH
Cu	2.50	4.500	Precipitation hardening agent — Cu-rich precipitates form on ageing
Nb	0.15	0.450	CB (Columbium/Niobium) — forms NbC carbides; controls grain size and reduces sensitisation. Distinguishes 15-5 PH from 17-4 PH (which uses Nb also, but different ratio)
Mn	—	1.000
Si	—	1.000
C	—	0.070
P	—	0.040
S	—	0.030

Mechanical & thermal properties — 4 conditions

Property	LPBF as-built (XY)	LPBF + H900 (480°C / 1h / AC) (XY) — peak strength	LPBF + H900 (Z)	LPBF + H1025 (552°C / 4h / AC) (XY) — balanced
Elastic modulus	190–205 GPa	—	—	—
Yield strength (0.2%)	820–1030 MPa	1170–1280 MPa	1020–1180 MPa	1000–1090 MPa
Ultimate tensile strength	950–1180 MPa	1280–1380 MPa	1130–1290 MPa	1070–1160 MPa
Elongation at break	12.0–26.0 %	6.0–12.0 %	4.0–12.0 %	10.0–18.0 %
Fatigue strength	—	530–720 MPa	—	—
Density	7.78 g/cm³	—	—	—
Relative density	99.0–99.9 %	—	—	—
Thermal conductivity	13.0–15.2 W/m·K	—	—	—
CTE	10.2–11.4 µm/m·K	—	—	—
As-built surface Ra	7.0–18.0 µm	—	—	—

Values shown as min–max where a spread is reported, otherwise as typical ± unit. Ranges reflect inter-source variation, not single-sample scatter. All values are for AM-processed specimens unless noted.

Engineering considerations

Austenite retention management: the most critical process control issue for LPBF 15-5 PH. Measure retained austenite by XRD on witness coupons from every build before accepting parts. Target <5% retained austenite after H900. If >10%, consider cryogenic treatment (-73°C/1h between HT steps) or re-optimise build parameters to reduce cooling rate variation.
Heat treatment protocol for H900: (a) remove from build plate after stress relief at 650°C/2h in Ar; (b) solution treatment is not required for most applications — go directly to ageing; (c) age at 480°C ±10°C / 1h / air cool. Temperature accuracy is critical — a 10°C increase reduces UTS by ~20 MPa. Calibrate furnace before each batch.
Machining strategy: machine in over-aged condition (H1150, 621°C/4h) if significant stock removal is needed. H1150 is near-annealed soft condition (~820 MPa UTS, ~1 HRC) — much easier to machine than H900. Re-age to H900 after machining. Final dimensions after re-age will change by <0.05% — account for in tolerance planning.
Corrosion: passivation per ASTM A380 or ASTM A967 after final machining to maximise corrosion resistance. Avoid contact with chlorides in service — 15-5 PH will pit and stress-corrosion-crack in H900 condition at high chloride concentrations (>100 ppm) and elevated temperature.
Surface integrity for fatigue: as-built LPBF surface (Ra 10–18 µm) must be machined or finished for fatigue-critical surfaces. Shot peening after machining can introduce beneficial compressive residual stress — increases fatigue limit by 20–30% for H900 condition.
Phase stability: 15-5 PH is susceptible to sensitisation if held at 400–650°C for extended periods (>100h) — Cr₂₃C₆ precipitates at grain boundaries deplete Cr, reducing corrosion resistance. Avoid prolonged service in this temperature range. H900 service temperature should not exceed 340°C for extended operation.
Part qualification: for aerospace structural 15-5 PH LPBF parts, use AMS 7008 as a framework (substituting 15-5 PH composition limits) plus OEM-specific property requirements. X-ray CT inspection for internal defects, FPI for surface cracks, and CMM for dimensional verification are standard.

Advantages

Highest strength of common AM stainless steels — H900 UTS ~1310 MPa vs. 316L ~600–700 MPa
Good corrosion resistance — better than 410/420 martensitic SS in atmospheric and mild acidic environments
Simple ageing cycle (480°C/1h) achieves peak H900 from as-built LPBF — no complex solution treatment needed
Better transverse toughness than 17-4 PH at equivalent strength — lower ferrite content in 15-5 PH vs. 17-4 PH
Good machinability in aged condition — cuts cleanly with carbide tooling vs. austenitic SS which work-hardens severely
LPBF parameter set is essentially identical to 17-4 PH — knowledge transfers directly
Multiple heat-treatment conditions (H900/H925/H1025/H1075/H1150) allow strength-toughness trade-off for each application
Non-magnetic in as-built state (retained austenite); near-fully magnetic after H900 (fully martensitic)

Limitations

Austenite retention in LPBF is a key risk: LPBF rapid cooling produces 10–30% retained austenite vs. <5% in wrought. Retained austenite reduces strength and causes property variability. Mitigation: cryogenic treatment (-73°C/1h) before ageing, or accept H900 properties below wrought minimum
Z-direction H900 UTS may not consistently meet AMS 5659 minimum (1310 MPa) — qualification testing in Z-direction is mandatory
H900 is brittle at low temperature — Charpy impact energy <14 J at -40°C. Not suitable for cryogenic applications or impact-critical applications in H900
Corrosion resistance is inferior to 316L in chloride-rich environments — use 316L or super-duplex for marine and offshore
High hardness in H900 (44 HRC) makes machining difficult — machine in over-aged (H1150) condition if complex machining is needed, then re-age
Residual stress in LPBF as-built is significant — stress relief before removal from build plate is recommended for complex parts
No dedicated AM 15-5 PH standard — AMS 7008 (17-4 PH) is used as proxy, adding qualification complexity
Magnetism: H900 condition is strongly magnetic — may interfere with precision sensors and MRI environments

Typical applications

Aerospace structural frames, brackets, and fittings — H900 condition for primary structureValve bodies and manifolds for oil & gas applications — H1025 for toughness in sour serviceMedical device housings and surgical instrument handles — biocompatible SS with high strengthPump shafts, impellers, and rotating equipment componentsTooling and fixtures requiring high strength and dimensional stabilityDefence structural components and weapon system hardwareNuclear fuel handling equipment requiring high strength and corrosion resistancePrecision machined components where tight dimensional tolerances are required after printing

Industries

aerospacedefenceoil-gasmedicalindustrial

Standards & certifications

AMS-7008established

LPBF-produced 17-4 PH stainless steel for aerospace — directly applicable H900 and H1025 conditions; also used as process reference for 15-5 PH LPBF qualification

aerospacedefence

AMS 7008 is specifically for 17-4 PH (UNS S17400), but is widely used as qualification framework reference for 15-5 PH LPBF in aerospace until a dedicated 15-5 PH AM standard is published.

ASTM-F3049established

Powder feedstock characterisation for LPBF 15-5 PH

aerospacemedicaloil-gas

ISO-52904established

Process qualification for safety-critical metal PBF parts

aerospaceenergyoil-gas

NADCAP-AC7110-14established

NADCAP accreditation for metallic AM parts — required for aerospace flight-critical 15-5 PH parts

aerospace