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PH 13-8 Mo Stainless Steel (UNS S13800 XM-13)

UNS S13800 is a premium martensitic precipitation-hardening stainless steel engineered for ultra-high strength, exceptional fracture toughness, and superior resistance to stress-corrosion cracking. Produced via advanced dual-vacuum melting, this material ensures ultra-high purity and uniform mechanical properties, making it highly reliable for critical, high-load applications across key industries.

It is the ideal material choice for manufacturing high-strength medical tools, surgical instrument supports, and precision shafts, as well as aircraft structural and landing gear components, actuators, and fasteners. Furthermore, it is widely utilized for high-strength shafts, pump/valve parts, corrosion-resistant components, and high-performance robotics components such as high-load joint shafts, drive shafts, and structural connectors.

DIN EN 10088-1：
Stainless steels - Part 1: List of stainless steels
AMS 5629：
Steel Bars, Forgings, Tubing, and Rings, Corrosion Resistant, 13Cr - 8Ni - 2.3Mo - 1.1Al, Vacuum Induction plus Consumable Electrode Melted
ASTM F899：
Standard Specification for Wrought Stainless Steels for Surgical Instruments
ASTM A564：
Standard Specification for Hot-Rolled and Cold-Finished Age-Hardening Stainless Steel Bars and Shapes

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Chemical Composition

Element	C	Mn	P	S	Si	Cr	Ni	Al	Mo	N	Fe
Content (%)	≤0.05	≤0.20	≤0.010	≤0.008	≤0.10	12.25-13.25	7.50-8.50	0.90-1.35	2.00-2.50	≤0.01	Balance

Heat Treatment Conditions and Mechanical Properties

Solution Treatment

Condition	Heating Temperature	Holding Time（h）	Tensile Strength (MPa)	Yield Strength (MPa)	Elongation（4D）	Reduction of Area（%）	Hardness (HRC)
Solution Annealed	1700 ± 25 °F/925 ± 15 °C	1	/	/	/	/	≤38

Aging Treatment

Condition	Heating Temperature	Holding Time（h）	Tensile Strength (MPa)	Yield Strength (MPa)	Elongation（4D）	Reduction of Area（%）	Hardness (HRC)
Aged	950°F/510°C	4	≥1515	≥1415	10	45	≥45
Aged	1000°F/540℃	4	≥1415	≥1310	10	50	≥43
Aged	1025°F/550°C	4	≥1280	≥1210	11	50	≥41
Aged	1050°F/565°C	4	≥1210	≥1140	12	50	≥40
Aged	1100°F/595°C	4	≥1035	≥930	14	50	≥34
Aged	1150°F/620°C	4	≥930	≥620	14	50	≥30

Supply Forms

Available Form	Size Range	Surface Finish	Length (Customizable)	Tolerance (Customizable)	Delivery Condition
Plate	T0.5-T200.0mm	Milled	L:200/250/300 W:200/300/500/1000	-0.0/+1.0mm	Solution Annealed
Bar	φ1.0-φ200.0mm	Ground / Precision Ground	3M/PCS	h6-h9	Solution Annealed
Wire	φ1.0-φ3.0mm	Ground / Precision Ground	1M/PCS	h6-h9	Solution Annealed

Datasheet

Additional Info

A Brief History of 13-8MoPH Stainless Steel

13-8MoPH stainless steel, also known as PH 13-8Mo, UNS S13800 or XM-13, is a martensitic precipitation-hardening stainless steel.

The name ‘13-8Mo’ derives from its alloy composition: approximately 13% chromium, approximately 8% nickel, with the addition of molybdenum. It is not a standard general-purpose stainless steel, but rather a type of PH stainless steel better suited to high-strength precision components.

Compared to common precipitation-hardening stainless steels such as 17-4PH, 13-8MoPH places greater emphasis on toughness, transverse mechanical properties and resistance to stress corrosion cracking. Consequently, it is frequently used in high-load precision components such as shaft parts, pins, fastening-related components, drive system parts, structural fasteners and aerospace components.

How was the 13-8MoPH developed

The development of 13-8MoPH was primarily driven by the need to address a practical issue with high-strength stainless steel components: parts cannot simply be ‘hard’.

If a pin lacks sufficient strength, it may bend; if the material of a shaft component is too brittle, it may fracture; and if the performance of fastening components is unstable following heat treatment, this can also affect assembly and operational reliability.

To address these issues, 13-8MoPH utilises a base composition of approximately 13% chromium and 8% nickel, with the addition of molybdenum to enhance corrosion resistance and resistance to stress corrosion cracking. The material achieves its strength through a nickel-aluminium precipitation hardening system during ageing treatment. The low-carbon design also helps to reduce brittleness, allowing the material to retain a degree of toughness whilst maintaining high strength.

When age-hardened for 4 hours at 950°F / 510°C, 13-8MoPH can achieve a tensile strength of over 1515 MPa, a yield strength of over 1415 MPa, and a hardness of over 45 HRC. At the same time, it retains an elongation of 10% and a reduction of area of 45%.

If plasticity is prioritised over maximum strength for a component, a higher-temperature ageing condition may be selected. For example, in a 1050°F / 565°C ageing condition, strength is slightly lower, but elongation can be increased to 12% and reduction of area can reach 50%.

Early applications of 13-8MoPH

13-8MoPH was initially used primarily for aerospace and high-strength mechanical components.

Typical applications include aerospace components, aircraft structural parts, landing gear-related parts, drive system components, fastening-related parts, shaft components and pins. These parts are typically small in size but require the ability to bear loads, transmit motion, or remain stable under repeated loading.

Standard stainless steels may lack sufficient strength, whilst some high-hardness materials may be too brittle. The advantage of 13-8MoPH lies in its ability to retain good toughness and stability after heat treatment whilst maintaining high strength, making it suitable for such precision load-bearing components.

Current applications of 13-8MoPH

13-8MoPH stainless steel is primarily used for precision components requiring high strength, a certain degree of toughness, and stability after ageing.

Common applications include:

Aerospace: Aircraft structural components, landing gear-related parts, drive system components, pins, fastening-related components, valve components, fittings and high-strength precision components.

Medical instruments and device components: Surgical instrument components, orthopaedic instrument components, dental instrument parts, precision shaft components, guide pins, drive tools and reusable instrument components. 13-8MoPH is more suitable for tool and instrument components and is not recommended as the preferred material for implant applications.

Mechanical Engineering: High-strength shaft components, pins, locating pins, drive shafts, precision fixture components, load-bearing machined parts, and components requiring stable strength following heat treatment.

Industrial Applications: Valve stems, pump shafts, fittings, high-strength fasteners, and mechanical components subjected to loads, vibrations or repetitive motion in moderately corrosive environments.

13-8MoPH is not typically the material of choice for low-cost machined parts, severe corrosive environments or implant applications.

Sunxin’s 13-8MoPH Stainless Steel Supply Support

Sunxin supplies 13-8MoPH stainless steel in sheet, bar and wire forms, as well as custom cut sizes.

Sheets are available in thicknesses ranging from 0.5 mm to 200.0 mm, with a mill-finished surface and supplied in a solution-annealed condition. Bars are available in diameters ranging from 1.0 mm to 200.0 mm, with a polished or precision-polished surface finish, and are available with h6–h9 tolerance options. Wire is available in diameters ranging from 1.0 mm to 3.0 mm.

Sunxin is certified to the ISO 13485 and ISO 9001 quality management systems and supports batch management, traceability control, inspection coordination and quality documentation management.

Prior to production, it is recommended to confirm the ageing condition, target hardness, dimensions, tolerances, surface finish, inspection items and quality documentation.

For projects involving aerospace structural components, drive system components, medical instrument parts, precision shaft components, guide pins and fastening-related components, Sunxin can assist in confirming the material form, delivery condition and inspection documentation.

FAQs

Product FAQs

Why do buyers choose 13-8MoPH?

Buyers typically choose 13-8MoPH because components require not only high strength, but also toughness after ageing, resistance to stress corrosion, and stable mechanical properties. In the 950°F aged condition, its tensile strength can reach ≥1515 MPa, yield strength ≥1415 MPa, and hardness ≥45 HRC. It is commonly used in aerospace components, precision shafts, fasteners, valves, medical instrument parts and high-load engineering components.

What are the main advantages of 13-8MoPH?

The advantage of 13-8MoPH is that its strength, hardness and ductility can be adjusted by varying the ageing temperature. The 950°F aged condition offers higher strength and hardness. Ageing at higher temperatures, such as 1050°F, 1100°F or 1150°F, reduces strength and hardness but increases elongation, making it more suitable for components requiring ductility or lower hardness.

When should 13-8MoPH be chosen over 17-4PH?

13-8MoPH should be considered when a component requires a higher performance margin than standard 17-4PH, particularly for projects with higher demands on toughness, stress corrosion resistance or operating conditions. 17-4PH is suitable for many standard high-strength components. 13-8MoPH is better suited to aerospace, precision engineering or high-load applications.

Is 13-8MoPH always better than 17-4PH?

No. If a component requires only standard high strength and cost control is a priority, 17-4PH may be sufficient. 13-8MoPH is better suited to projects with higher requirements for strength grade, heat treatment condition, stress corrosion resistance or operational reliability. The final choice depends on the drawings, standards and actual operating conditions.

What is the difference between 950°F and 1050°F ageing?

950°F ageing is suitable for parts where strength and hardness are the primary priorities. In this condition, tensile strength is ≥1515 MPa, yield strength is ≥1415 MPa, elongation is 10%, and hardness is ≥45 HRC. At 1050°F, strength is reduced to a tensile strength of ≥1210 MPa and a yield strength of ≥1140 MPa, but elongation is increased to 12%.

When should 1100°F or 1150°F ageing be selected?

When parts do not prioritise the high strength of the 950°F condition, but require greater ductility and lower hardness, 1100°F or 1150°F ageing may be considered. In the 1100°F aged condition, tensile strength is ≥1035 MPa and elongation is 14%. In the 1150°F aged condition, tensile strength is ≥930 MPa, elongation is 14%, and hardness is ≥30 HRC.

How should one select the aged condition for 13-8MoPH?

The aged condition should be selected based on the component’s function. If the component requires greater strength and hardness, 950°F or 1000°F ageing should be considered. If the component requires greater ductility, lower hardness or more moderate mechanical properties, 1050°F, 1100°F or 1150°F ageing should be considered. The target strength, hardness, elongation and final service environment should be confirmed prior to procurement.

Should 13-8MoPH be purchased in the solution-treated or aged condition?

If the material requires further machining or post-processing, the solution-treated condition is recommended. In the solution-treated condition, the hardness is ≤38 HRC, making it more suitable for subsequent machining. If the final strength, hardness or mechanical properties are already specified, the appropriate aged condition may be selected.

Is 13-8MoPH easy to machine?

13-8MoPH is easier to machine prior to final ageing. After ageing, particularly in the 950°F or 1000°F condition, the material’s strength and hardness increase, making machining more difficult. For high-precision components, it is advisable to confirm the machining sequence, finishing allowances and final ageing condition in advance.

What information is required when enquiring about 13-8MoPH?

We recommend providing the material grade, applicable standards, product form, dimensions, tolerances, quantity, delivery condition, ageing condition, target strength or hardness, testing documentation requirements and end use. If the parts are intended for aerospace, medical instruments or high-load applications, drawings and operating conditions are essential.