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Materials/Metals and alloys/Stainless steels

Precipitation-hardening stainless steels

stainless-precipitation-hardening

3 materials across 1 types

About precipitation-hardening stainless steels

Precipitation-hardening stainless steels (17-4 PH): strength by heat-treatment condition, with sources.

Precipitation-hardening stainless steels gain strength from a low-temperature ageing treatment after solution annealing. Strength is set by the condition (A, H900, H1025, H1150), so values are listed by condition.

At a glance

  • Highest density: 17-4 PH stainless steel reaches 7.86 g/cm³. Lowest: 17-7 PH stainless steel starts at 7.65 g/cm³. (3 of 3 grades have a sourced value.)

Ranges run across the conditions each source reports (temper, heat treatment, form), measured at room temperature where the source says so.

How they compare

The same measurements for every material in the collection. A range means the grade has values under several conditions; "at least" means the source gives a specified minimum. "no data" means no sourced value yet. For ranked tables, open a benchmark.

Precipitation-hardening stainless steels: how the grades compare
MaterialYield strengthTensile strengthDensityYoung's modulusThermal conductivityMelting point
17-4 PH stainless steelprecipitation-hardening structural alloy 725 to 1,262 MPa930 to 1,365 MPa7.75 to 7.86 g/cm³196 to 201 GPa17.9 to 22.6 W/(m·K)1,404 to 1,440 °C
17-7 PH stainless steelhigh-strength semi-austenitic precipitation-hardening stainless steel 310 to 1,896 MPa827 to 2,034 MPa7.65 to 7.81 g/cm³200 GPa16.9 W/(m·K)1,404 to 1,440 °C
PH 15-7 Mo stainless steel (15-7 PH)Semi-austenitic precipitation-hardening stainless steel for high-strength springs, rings and aircraft parts 380 to 1,515 MPa860 to 1,690 MPa7.67 to 7.8 g/cm³200 GPa16.2 W/(m·K)no data

What these materials are made of

Composition by weight, as printed in the sources for each grade (the first constituents listed).

Composition of each grade
MaterialMain constituents
17-4 PH stainless steelFe balance · Cr 15 to 17.5% · Ni 3 to 5% · Cu 3 to 5% · Nb+Ta 0.15 to 0.45% · C up to 0.07% · Mn up to 1%
17-7 PH stainless steelFe balance · Cr 16 to 18% · Ni 6.5 to 7.75% · Al 0.75 to 1.5% · C up to 0.09% · Mn, Si, P, S up to 1.00%

Where they are used

Uses
UseGrades
Aircraft and missile fittings17-4 PH stainless steel
Bolts and fasteners17-4 PH stainless steel
Jet engine stator vanes17-4 PH stainless steel
Reaction-motor and support-equipment fittings for rocket-driven spacecraft17-7 PH stainless steel
Flat springs, Belleville (conical spring) washers and eyelets17-7 PH stainless steel
Aerospace bulkheads, retaining rings and tooling17-7 PH stainless steel
Springs and spring-type partsPH 15-7 Mo stainless steel (15-7 PH)
Seal rings and retaining ringsPH 15-7 Mo stainless steel (15-7 PH)
Aircraft componentsPH 15-7 Mo stainless steel (15-7 PH)

When each grade fits

Best use and weak spots of each grade
MaterialBest forWeakest at
17-4 PH stainless steelHigh-strength fittings, fasteners, shafts and valve parts that need more strength than 304 and moderate corrosion resistanceStress corrosion cracking and pitting in peak-aged (H900) material, and crevice corrosion in stagnant salt water
17-7 PH stainless steelSprings, Belleville washers, eyelets and flat springs that need high strength and stainless corrosion resistance, with formability in the soft stateStress corrosion cracking in chloride and in nitrogen tetroxide/hydrazine propellant, in every heat-treated condition except CH 900; ductility in CH 900 (2 % elongation)
PH 15-7 Mo stainless steel (15-7 PH)Springs, retaining rings and seal rings that need high strength with a low-distortion hardening heat treatment (ATI and Ulbrich list these uses)Stress corrosion cracking in salt water: the 1969 NASA test found the alloy cracked in all conditions except CH 900, and corrosion resistance is below Type 304 (ATI)