Selection summary
Overview
17-4 PH is a martensitic precipitation-hardening stainless strengthened by solution treatment and aging. It is widely used for shafts, valves, fasteners, aerospace parts, and tooling where strength exceeds that of annealed austenitic grades, but properties and corrosion behavior depend strongly on heat-treatment condition.
This page separates standard-oriented limits from typical reference data. Purchase acceptance comes from the ordered specification and certified material test report.
Names and systems
Identity & standards
Similar designations across ASTM, EN, JIS, and other systems are not automatically interchangeable. Product form and ordered standard control chemistry, properties, dimensions, condition, and testing.
Reference chemistry
Composition
| Element | Reference range | Why it matters |
|---|---|---|
| Chromium | 15.0–17.5% | Corrosion and oxidation resistance |
| Nickel | 3.0–5.0% | Transformation and toughness control |
| Copper | 3.0–5.0% | Precipitation hardening |
| Niobium + tantalum | 0.15–0.45% | Strengthening response |
Concise grade-family reference only. Confirm every element limit against the current standard for the exact product ordered.
Condition matters
Reference properties
Specify solution/aging condition such as H900 or H1150
Heat treatment can change strength and toughness substantially
Typical room-temperature reference
Environment first
Corrosion behavior
Generally useful in many atmospheric and mild process environments, but not a substitute for highly alloyed grades.
Heat treatment, surface finish, stress, and marine exposure must be reviewed together.
Temperature, concentration, deposits, crevices, stress, surface finish, cleaning, and fabrication quality can change service performance.
Service limits
Temperature & service
Strength, toughness, stress-corrosion behavior, and dimensional change depend on the aging condition.
Delivery condition
Heat treatment & condition
17-4 PH is solution treated to Condition A and then precipitation aged to an explicitly ordered condition such as H900, H1025, H1150, or a specification-defined variant.
Strength, toughness, corrosion behavior, distortion, and stress-corrosion performance change with aging condition; property values must identify both product form and condition.
Process route
Fabrication
Usually machined in solution-treated or overaged conditions selected for the process route.
Welding is possible, but pre-weld condition and post-weld aging govern final properties.
Magnetic response: Ferromagnetic.
Decision boundaries
Comparisons & substitution
17-4 PH provides much higher age-hardened strength than annealed 304/316, but it is not selected as a universal substitute for their corrosion or fabrication behavior.
More highly overaged conditions generally trade some strength for greater toughness and stress-corrosion margin; the governing specification controls acceptance.
Where it is used
Applications
Ordering scope
Product forms & standards
Bars, shapes, and forgings supplied in Condition A or an ordered aged condition under the applicable product specification.
Plate, sheet, and strip where the product standard includes UNS S17400 and the required heat-treatment condition.
Machined components must retain heat identity and condition records through any subcontracted solution treatment or aging cycle.
Decision support
Selection guidance
Choose this grade when
- High strength and dimensional stability are needed with moderate stainless corrosion resistance.
- The supplier can certify the exact heat-treatment condition and test results.
Review another grade when
- Maximum chloride or acid resistance matters more than strength.
- Low-temperature toughness or welding dominates without a qualified heat-treatment route.
Before ordering
Procurement checklist
Name the governing product standard, edition, dimensions, tolerances, edge, finish, and delivery condition.
Require the exact UNS designation and a material test report; a familiar trade name alone is not an acceptance criterion.
Confirm corrosion environment, design temperature, fabrication route, inspection, certification, marking, and packaging before order release.
State the required heat-treatment condition, hardness or strength range, and any post-machining aging or straightness requirement.
Traceable evidence