17-4 PH — what the data actually supports

Data completeness: partial. Last verified 19 August 2026.

Designations

17-4 PH is the most specified precipitation hardening stainless there is, and it is also the grade where a number quoted without its condition is closest to meaningless. The same alloy runs from roughly 750 MPa proof strength in the solution treated state to well over 1100 MPa in the shortest ageing treatment, and the condition code — H900, H1025, H1150 and the rest — is not an adjective but the specification. The datasheet consulted for this page prints no condition column at all, which is why every mechanical row below carries that gap explicitly and why the page is a demonstration as much as a data sheet.

Properties, with what each one rests on

7 sourced values, 4 gaps named. Publishing the gaps is more useful than filling them from an aggregator that does not say where its numbers came from. The routes to filling them are the standard itself, a mill datasheet, or a mill certificate for your actual heat — which supersedes both at E5.

Where the numbers come from

Proof strength Rp0.2, typical. Use this to know roughly what family of strength the alloy lives in, and for nothing else. Without the ageing condition it cannot be checked, cannot be reproduced and cannot go on a drawing. The bar row in the same table is 600 MPa — a 42% spread inside one grade in one document, and the datasheet offers no way to tell whether that is product form, condition or both.

Tensile strength Rm, typical. The highest strength figure anywhere in this data set, roughly double what 2507 super duplex offers and four times 316L. That is what precipitation hardening is for.

Why we do not just copy an aggregator. Because then this page would be a worse copy of MatWeb with no way for you to tell which rows to trust, and the one thing we have that MatWeb does not is the evidence column. Our coverage and its limits.

What 17-4 PH is usually chosen for

Parts that need high strength, moderate corrosion resistance and dimensional stability through hardening. Pump and valve shafts, aerospace fittings, injection moulds, firearm and turbine components. It is machined soft and aged afterwards at a low enough temperature that the part barely moves, which is the property that distinguishes it from a quenched martensitic grade.

And what it is usually rejected for

Chlorides, temperature and toughness at the top of its range. Its corrosion resistance sits between 410 and 304, nowhere near 316L, and the shortest ageing treatments trade notch toughness and stress corrosion resistance for strength. Above roughly 300 °C the precipitates that give it strength begin to over-age, and no source consulted for this page covers that.

The number to be more careful with than any of the above is the difference between a specified minimum and a typical value — a floor the standard guarantees, versus what a supplier’s production usually does. The full version, and the most expensive routine mistake in material data.

Compare

17-4 PH vs 17-7ph · 17-4 PH vs 316l

What this page does not cover

• The heat treatment condition, which for this alloy is the difference between two grades’ worth of strength.
• No specified minima. Everything here is a mill typical value and cannot be used as a design allowable.
• No hardness values.
• No corrosion data, and the alloy is often chosen where 316L would be safer.
• Behaviour above roughly 300 °C, where the ageing that gives it strength starts to reverse. No source consulted here covers it.

Generated from data/materials/17-4ph.yaml. Regenerate rather than editing this file by hand — edits here are lost on the next build.