17-4 PH vs. 15-5 PH vs. 13-8 PH Stainless Steel

September 24, 2026
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17-4 PH vs. 15-5 PH vs. 13-8 PH Stainless Steel: Similarities, Differences, and Applications

13-8PH, 15-5PH, 17-4PH, Material Selection, PRODEC 17-4, Stainless Steel, Technical

When selecting a high-strength stainless steel for demanding engineering applications, three precipitation-hardening grades frequently rise to the top: 17-4 PH,15-5 PH, and 13-8 PH. These martensitic age-hardenable alloys offer high strength, corrosion resistance, and versatile mechanical properties, making them valuable across a range of industries.

While these grades share several important characteristics, differences in composition, processing methods, mechanical performance, and cost can influence material selection. This article examines the key similarities and differences among 17-4 PH,15-5 PH, and 13-8 PH, as well as fabrication considerations and typical applications.

What Do 17-4 PH, 15-5 PH, and 13-8 PH Have in Common?

17-4 PH, 15-5 PH, and 13-8 PH are all iron-based stainless steels classified as martensitic age-hardenable grades. Unlike 400 series stainless steels, which achieve strength through quenching and tempering, these alloys are strengthened through an aging process. During aging, the material is held at a specific elevated temperature for a designated period, allowing precipitates to form within the microstructure, which heavily influence mechanical properties.

Typical supplied condition

These materials are typically supplied in the annealed condition, commonly identified as Condition A on material test certificates. This condition allows for subsequent aging treatments to achieve the desired mechanical characteristics, catering to a wide range of needs. Other commonly available aged conditions include 17-4 H1075, 17-4 H1150, and 15-5 H1025.

Significance of How PH Grades Are Named

These alloys follow a consistent naming convention in which the first number represents chromium content, while the second represents nickel content. For example, 17-4 contains 17% chromium and 4% nickel.

Cutting Considerations

One important consideration when using these alloys is the selection of the cutting method. Due to the potential for untempered martensite to form at cut edges, thermal cutting is not recommended for these grades. Instead, cold-cutting methods should be used, including:

• Bar saw cutting
• Waterjet cutting
• Band saw cutting
• Shearing

These methods help reduce brittleness and minimize the risk of fractures.

Fabrication and Weldability

When evaluated under similar conditions, all three alloys exhibit comparable machinability. Their fabrication and weldability characteristics are also broadly similar. However, welding can create localized variations in mechanical properties, potentially making post-weld heat treatment necessary to obtain desired performance.

What are the differences between 17-4 PH, 15-5 PH, and 13-8 PH Stainless Steel?

Precipitation Strengthening Mechanisms

The primary strengthening mechanism during aging differs between the grades.

• 17-4 PH and 15-5 PH develop copper-rich precipitates within the martensitic matrix.
• 13-8 PH uses aluminum rather than copper, forming nickel-aluminum precipitates.

Melting and Production Processes and Cost Considerations

The melting routes vary significantly among the three grades:

Application Scope

Application requirements often determine which alloy is selected.

17-4 PH is commonly used in less critical and industrial applications.

15-5 PH and 13-8 PH are typically chosen for more demanding applications that require enhanced material performance.

Enhanced-Machining Option: PRODEC® 17-4

Among these grades, 17-4 PH is unique in offering an enhanced-machining variant.

At Rolled Alloys, PRODEC® 17-4 is stocked to improve productivity and machining efficiency. It supports higher cutting speeds and feeds with reduced tool wear, and meets standard 17-4 PH ASTM, AMS, and ASME specifications.

Dive Deeper into PRODEC® Stainless Steel Bar

Learn how PRODEC machining-grade stainless steel bars can help improve part quality, increase machining speeds, and lower overall production costs.

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Mechanical Properties After Aging

The alloys exhibit a wide range of mechanical property profiles after aging treatments.

13-8 PH tends to provide superior ductility and improved transverse-direction performance.

13-8 PH Stainless Steel Typical Mechanical Properties*

PROPERTY	A	H950	H1000	H1050	H1100	H1150	H1150-M
UTS, ksi	16 0	225	215	190	160	145	130
0.2% YS, ksi	12;0	210	205	180	150	105	85
Elongation, % in 2"	-	12	13	15	18	18	22
Hardness, Rockell C	33	47	45	43	35	35	32

*Small Diameter Bar Typical Values (1-3″); Data Source: Cleveland-Cliffs.

15-5 PH offers ductility levels that closely follow 13-8 PH.

15-5 PH Stainless Steel Typical Mechanical Properties*

PROPERTY	A	H900	H925	H1025	H075	H1150	H1150-M
UTS, ksi	16;1	209	181	174	162	150	136
0.2% YS, ksi	14; 0	201	175	171	160	140	111
Elongation, % in 2"	8	10	12	12	13	15	19
Hardness, Rockell C	35	46	41	40	38	36	31

*Cold-flattened sheets and strip; Data Source: Cleveland-Cliffs.

17-4 PH generally exhibits lower ductility compared with the other two grades.

17-4 PH Stainless Steel Typical Mechanical Properties*

PROPERTY	A	H900	H925	H1025	H075	H1150	H1150-M
UTS, ksi	16;0	210	200	185	175	160	150
0.2% YS, ksi	15; 5	200	195	170	165	150	130
Elongation, % in 2"	5	7	8	8	8	11	12
Hardness, Rockell C	35	45	43	38	37	35	33

*Cold-flattened sheets and strip; Data Source: Cleveland-Cliffs.

Which PH Stainless Steel Should You Choose?

Selecting between 17-4 PH, 15-5 PH, and 13-8 PH depends on the balance of mechanical properties, ductility, production requirements, machining considerations, and cost required for the application. While all three are precipitation-hardening stainless steels, their differences in melting practice and mechanical performance can influence which grade is the best fit.

Feature	17-4 PH	15-5 PH	13-8 PH
Primary Hardening Mechanism	Copper-rich precipitates	Copper-rich precipitates	Nickel-Aluminum precipitates
Typical Production Method	Air Melt	Air Melt + VAR/ESR	VIM + VAR/ESR
Relative Cost	Lowest	Medium	Highest
Ductility	Good	Better	Best
Typical Application Scope	Industrial, Less Critical Applications	Critical Applications	High-Demanding Applications
Common Applications	Industrial equipment, Valves, Pumps, Fasteners, Firearms, Aerospace, Space, and Defense components	Aerospace, Defense, Space, Nuclear components, Fasteners, and high-strength structural applications	Aerospace, Defense, Space, Nuclear components, Fasteners, and high-strength structural applications
Enhanced Machining Grade Available	Yes (PRODEC® 17-4)	No	No

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17-4 PH vs. 15-5 PH vs. 13-8 PH Stainless Steel

Compare 17-4 PH, 15-5 PH, and 13-8 PH stainless steel in terms of mechanical properties, melting methods, ductility, machinability, cost, and applications.

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