Stainless Steel, Precipitation Hardening
3S144 (S144) Bar
Aerospace-grade precipitation hardening stainless steel.
S144 is a British aerospace grade, precipitation hardenable stainless steel. It is widely used in the aerospace industry benefiting from a combination of strength and moderate corrosion resistance.
The alloy has an identical chemical composition when compared to S143 but a higher tensile strength is achieved as a result of heat treatment.
DOWNLOAD PDF
Range
PLEASE NOTE
To enquire about our range or your specific requirements, please contact your local service centre.
3S144 Stainless Steel Related Specifications
| System / Standard | Country / Region | Grade / Designation |
| BS Aerospace S100 | UK | 3S144 (S144 bar) |
| EN / W.Nr. | Europe | 1.4594 |
| EN Name | Europe | X5CrNiMoCuNb14-5 |
| UNS | International | S45000 |
| Trade name | International | FV520B |
| GB | China | 0Cr14Ni5MoCuNb |
Properties
Chemical Composition
| Chemical Element | % Present |
| Carbon (C) | 0.00 - 0.08 |
| Chromium (Cr) | 13.20 - 14.70 |
| Nickel (Ni) | 5.00 - 5.80 |
| Manganese (Mn) | 0.00 - 1.00 |
| Phosphorous (P) | 0.00 - 0.04 |
| Sulphur (S) | 0.00 - 0.03 |
| Silicon (Si) | 0.00 - 0.60 |
| Niobium (Columbium) (Nb) | 0.10 - 0.40 |
| Molybdenum (Mo) | 1.20 - 2.00 |
| Copper (Cu) | 1.20 - 2.00 |
Mechanical Properties
| Mechanical Property | Value |
| Tensile Strength | 1130-1330 MPa |
| Elongation A50 mm | 12 % |
| Hardness Brinell | 341 HB |
| Tensile Strength | 1030 N/mm2 |
Applications of S144 / 3S144 Stainless Steel Bar
1. Aerospace Structural and Rotating Components
S144 / 3S144 bar is primarily used in aerospace and defence hardware where very high strength and reliable toughness are required together with moderate corrosion resistance. Typical parts include:
Highly stressed shafts and spindles
Actuation components and control system parts
Pins, levers and clevis fittings in flight control and landing systems
Other safety-critical structural items in airframes and engines
2. High-Performance Mechanical and Power-Transmission Parts
Thanks to its combination of high tensile strength, wear resistance and fatigue performance, 3S144 is widely used for power-transmission and rotating components, such as:
Pump and compressor shafts, impellers and rotors
Couplings, hubs and flanges
Precision gears and rings operating under high contact stress
Components in gas turbines, compressors and auxiliary power units
3. Precision Fasteners and Fittings
The alloy’s high strength and good galling resistance make it suitable for precision fasteners and fittings in demanding environments, including:
High-strength bolts, screws and studs
Bushes, sleeves and bearing races
Hydraulic fittings and connector hardware in aerospace and high-tech machinery
4. Corrosion-Resistant High-Load Components
In mildly corrosive or marine-influenced environments where loads are high, S144 / 3S144 bar is selected for:
Valve components and actuator parts
Marine and offshore mechanical hardware exposed to splash and atmospheric corrosion
General engineering parts requiring a combination of stainless corrosion resistance and very high mechanical strength
5. Defence and High-Integrity Engineering
As a British aerospace grade specified in BS S100, S144 / 3S144 is also widely used in defence and high-integrity engineering, including:
Critical weapon system components and guidance hardware
High-reliability parts in military vehicles and equipment
Other mission-critical mechanisms where consistent properties and traceable heat treatment are mandatory
One-Sentence Summary
S144 / 3S144 stainless steel bar is used mainly for highly loaded aerospace, defence and high-performance mechanical components—such as shafts, rotors, fasteners, actuators and precision fittings—where very high strength, excellent wear and galling resistance, and dependable corrosion performance are required.
Characteristics of 2S143D / S143 Stainless Steel Bar
1. Precipitation-Hardening Martensitic Stainless Steel
2S143D / S143 is a Cu + Nb precipitation-hardening martensitic stainless steel, designed to achieve high mechanical strength through controlled aging.
2. High Strength After Aging Treatment
After solution treatment and double-stage aging, the alloy provides:
High tensile strength: approx. 930–1180 MPa
High yield strength: around 780 MPa
High hardness with excellent load-bearing capability
Suitable for highly stressed structural components.
3. Good Corrosion Resistance
Corrosion resistance is better than conventional martensitic grades (e.g., 420/440) and adequate for aerospace and mechanical applications, though slightly below that of Cr-rich PH grades like 17-4PH.
4. Excellent Galling and Wear Resistance
Owing to its alloying with Mo and Cu, S143 exhibits:
Outstanding anti-galling performance
Good resistance to wear and fretting corrosion
Stable surface performance under sliding contact
Ideal for components with repeated mechanical interaction.
5. Stable Mechanical Properties & Fatigue Performance
The alloy offers:
Stable microstructure after aging
Balanced toughness and strength
Reliable fatigue resistance under cyclic loading
Frequently selected for high-integrity aerospace parts.
6. Good Machinability in Bright Bar Condition (2S143D)
The suffix “D” indicates Bright Drawn Bar, providing:
High dimensional accuracy
Smooth surface finish
Good machinability for precision CNC operations
Suitable for tight-tolerance mechanical parts
7. Fully Magnetizable Material
As a martensitic PH stainless steel, S143 is magnetic, which may be relevant for applications involving sensors or magnetic systems.
8. Aerospace-Grade Reliability
S143 was developed for aerospace and defense use and provides:
High reliability
Consistent properties
Proven performance in critical flight hardware
Characteristics of 3S144 / S144 Stainless Steel Bar
1. Precipitation-Hardening Martensitic Stainless Steel
3S144 / S144 is a Cu + Nb precipitation-hardening martensitic stainless steel bar grade, developed within the BS S100 aerospace series to deliver very high strength through controlled solution treatment and ageing. It has the same basic chemistry as S143, but is heat treated to a higher strength level.
2. Very High Strength After Aging Treatment
After solution treatment and low-temperature ageing, the alloy provides:
Very high tensile strength: typically about 1130–1330 MPa
High yield strength: typically ≥ 1030 MPa (0.2% proof)
High hardness: approximately 352–401 HB
This strength level, combined with good toughness, makes 3S144 suitable for highly stressed structural and rotating components in aerospace and advanced mechanical systems.
3. Good Corrosion Resistance
The corrosion resistance of 3S144 is:
Better than standard martensitic grades such as 420 / 440 in most industrial and mildly marine environments
Comparable to or slightly below austenitic grades like 304 in many atmospheric conditions
Adequate for long-term use in aerospace, marine, and general engineering applications where high strength plus corrosion resistance are required
However, its corrosion resistance is somewhat lower than that of higher Cr PH grades (e.g., 17-4PH / SUS630) and it is not intended for the most aggressive chloride environments.
4. Excellent Galling and Wear Resistance
Due to alloying additions of Mo, Cu and Nb and its hardened martensitic + precipitate microstructure, 3S144 offers:
Outstanding anti-galling performance
Very good wear and fretting corrosion resistance
Stable surface behaviour under sliding or oscillating contact
These features make it ideal for shafts, bearings, fasteners, couplings and actuation components subject to repeated mechanical interaction.
5. Stable Mechanical Properties & Fatigue Performance
The alloy exhibits:
A stable, fine precipitation-hardened microstructure after ageing
A well-balanced combination of high strength and useful toughness
Reliable fatigue performance under cyclic loading
As a result, 3S144 is widely selected for high-integrity aerospace and defence hardware, including safety-critical components.
6. Bar Condition and Machinability
3S144 is typically supplied as bright drawn or ground bar and forgings for machining:
Good dimensional accuracy and straightness
Smooth surface finish suitable for precision turning, grinding and polishing
Reasonable machinability for CNC operations, though generally more difficult to machine than austenitic grades such as 304 due to its higher hardness and strength
It is well suited to tight-tolerance mechanical parts that are finish-machined after heat treatment or supplied in a machinable condition followed by final ageing.
7. Fully Magnetizable Material
As a martensitic PH stainless steel, 3S144 is fully magnetic in all heat-treated conditions. This can be important in applications involving magnetic couplings, sensing, or assembly using magnetic tools and fixtures.
8. Aerospace-Grade Reliability
Developed specifically for aerospace and defence applications within the BS S100 series, 3S144 provides:
Aerospace-grade reliability and consistency
Tight control of chemistry, cleanliness and heat treatment
A long track record of proven performance in critical flight and defence hardware, such as shafts, fasteners, and actuation components
One-Sentence Summary
3S144 is a very high-strength, Cu + Nb precipitation-hardening martensitic stainless steel bar grade with excellent galling and wear resistance, good corrosion resistance, stable fatigue performance and aerospace-grade reliability, ideal for highly loaded precision components in demanding mechanical and aerospace applications.
