15-5 Stainless Steel CNC Machining for Performance
15-5 PH stainless steel is a precipitation-hardening martensitic alloy used across aerospace, defense, and industrial applications where high strength, corrosion resistance, and transverse toughness are required in the same component. Its combination of mechanical properties makes it a frequent specification on structural aerospace hardware, valve components, and high-load mechanical assemblies.
Carr Machine & Tool machines 15-5 PH stainless steel for aerospace and defense customers from our facility in Elk Grove Village, Illinois. We machine 15-5 in all heat treat conditions, from H900, H925, H1025, H1075, H1100, to H1150, with material-specific process planning, AS9100D-certified quality documentation, and full material traceability.
UNDERSTANDING 15-5 PH Stainless Steel
COMPOSITION & PROPERTIES
15-5 PH (UNS S15500) is a chromium-nickel-copper precipitation-hardening stainless steel. Its nominal composition is approximately 15% chromium, 5% nickel, and additions of copper and niobium. It produces a martensitic microstructure after solution annealing that can be further strengthened by aging heat treatments.
Key properties that make 15-5 PH a design choice for aerospace and defense components:
- High Tensile & Yield Strength: Yield strength ranges from approximately 115 ksi in the H1150 condition to over 200 ksi in the H900 condition
Good corrosion resistance — Performs significantly better than standard martensitic grades; approaches 304L in corrosion resistance in some environments - High Transverse Toughness: Produced as a vacuum induction melted (VIM) or vacuum arc remelted (VAR) alloy, which significantly reduces sulfide inclusions and improves toughness in the transverse direction versus 17-4 PH
- Good Fatigue Resistance: Higher fatigue strength than comparable austenitic stainless grades at equivalent hardness
- Magnetic: Martensitic structure is ferromagnetic; relevant for applications where magnetic behavior must be considered
15-5 PH VS. 17-4 PH STAINLESS STEEL
Both are precipitation-hardening stainless steels with similar heat treat designations and overlapping applications. The primary distinction is in transverse toughness. 15-5 PH is processed to achieve better toughness in the transverse direction, which is the direction perpendicular to the rolling or forging direction of the bar stock. For components where the critical stress path runs transverse to the grain, like those particularly machined aerospace fittings cut from bar, 15-5 PH is often specified over 17-4 PH for this reason.
HEAT TREATMENT CONDITIONS WE MACHINE
We machine 15-5 PH in all of these conditions. The heat treat condition affects both the machining parameters and the inspection requirements. Harder conditions require adjusted tooling and feeds, and hardness verification is included in our inspection protocol where your drawing specifies a condition requirement.
| Condition | Approx. Yield Strength | Typical Applications |
|---|---|---|
| H900 | 200+ ksi | Maximum strength, limited toughness — highly stressed structural parts |
| H925 | ∼175 ksi | High strength with improved toughness over H900 |
| H1025 | ∼155 ksi | Balance of strength and corrosion resistance — common aerospace spec |
| H1075 | ∼145 ksi | Further improved toughness; good general purpose structural condition |
| H1100 | ∼135 ksi | Good corrosion resistance, improved ductility |
| H1150 | ∼115 ksi | Highest toughness and ductility; applications requiring impact resistance |
Material Knowledge That Drives Quality
15-5 PH in the annealed condition (Condition A) machines similarly to 304 stainless. In aged conditions, particularly H900 and H925, it behaves more like a hardened alloy steel and requires corresponding tooling and parameter adjustments.
Key machining considerations our process team manages:
- Work Hardening: Like most stainless alloys, 15-5 PH can work-harden if feed rates are too low or the cutting edge dwells without advancing. We program feeds to maintain positive chip formation through the full cut.
- Heat Generation: Stainless alloys generate heat at the cutting zone due to lower thermal conductivity than carbon steel. Flood coolant strategy and cutting parameter selection prevent thermal damage to the workpiece and maintain surface finish requirements.
- Tooling Selection: Carbide tooling with appropriate geometry for stainless is used rather than general-purpose tooling. In harder heat treat conditions, tooling selection is adjusted accordingly.
- Surface Finish: 15-5 PH can achieve excellent surface finish with the right tooling and finishing passes. Ra requirements down to 16 µin and finer are achievable with appropriate process planning.
Integrated Quality and Documentation
- Material Certifications: We source 15-5 PH from certified suppliers with full chemistry certifications per the applicable AMS specification (typically AMS 5659 for bar and AMS 5826 for other product forms). Certifications are retained and tied to your job traveler.
- Hardness Verification: For drawings that specify a heat treat condition with hardness requirements, we verify hardness after machining and document results in our inspection records. Hardness testing equipment is calibrated per our AS9100D quality system.
- First Article Inspection: Every new 15-5 PH program receives a complete FAIR with actual measured values for every drawing callout. FAIRs are formatted to your program requirements and provided with the first shipment.
- Special Process Coordination: If your drawing requires special processes on 15-5 PH components — passivation, electropolishing, plating, anodize, or non-destructive testing. We coordinate with qualified special process suppliers as part of the job. Special process certifications are included in your job documentation package.
FREQUENTLY ASKED QUESTIONS
What is the AMS specification for 15-5 PH bar stock?
15-5 PH bar is typically procured to AMS 5659. Other product forms are covered by additional AMS specifications. We source material to the specification called out on your drawing and provide mill certifications with every job.
Can you machine 15-5 PH in the H900 condition?
Yes. H900 is the hardest and strongest condition for 15-5 PH. Machining in this condition requires adjusted tooling and cutting parameters compared to the annealed condition, but we have production experience machining H900 parts to aerospace tolerances. For complex parts, it is often more economical to machine in Condition A or H1025 and age to H900 after machining. We can discuss the trade-off for your specific geometry during the quoting process.
How does 15-5 PH compare to 17-4 PH for aerospace applications?
15-5 PH offers better transverse toughness than 17-4 PH at equivalent strength levels, which makes it the preferred choice for many aerospace structural fittings cut from bar where the primary loading is transverse to the bar’s rolling direction. Strength levels, heat treat designations, and machinability are similar between the two alloys.
Do you provide passivation for 15-5 PH parts?
We coordinate with qualified special process suppliers for passivation, typically per ASTM A967 or AMS 2700. Special process certifications are included in your documentation package. Inform us of any passivation or finishing requirements during the quoting process so we can include special process coordination in the timeline and cost.
What surface finish can you achieve on 15-5 PH?
We regularly achieve Ra 32 µin or better on milled surfaces and Ra 16 µin or better on turned surfaces as-machined. Finer surface finish requirements — Ra 8 µin or Ra 4 µin — are achievable on specific features with planned finishing passes and appropriate tooling. Surface finish is verified with profilometer measurement where your drawing specifies a callout.
Partner with CARR Machine & Tool
Submit your drawing and program requirements. We will review your geometry, heat treat condition, and any special process requirements and return a complete quote with lead time.
