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Defence & Aerospace Grades

Defence and aerospace applications demand materials that can withstand extreme stress, high temperatures, corrosion, and fatigue. Materials used must meet stringent international standards for strength, durability, and performance.



EN24 Steel (817M40)


Standard: BS 970-1955: EN24 / BS 970-1991: 817M40

Application: Widely used in the defence and aerospace industries for parts that require high tensile strength, toughness, and shock resistance.


Chemical Composition (%):
Element Content
Carbon (C)0.36 – 0.44%
Silicon (Si)0.10 – 0.35%
Manganese (Mn)0.45 – 0.70%
Chromium (Cr)0.90 – 1.40%
Nickel (Ni)1.30 – 1.80%
Molybdenum (Mo)0.20 – 0.35%
Phosphorus (P)≤ 0.035%
Sulfur (S)≤ 0.040%
Properties:
  • High tensile strength and shock resistance
  • Excellent toughness and fatigue resistance
  • Good ductility and dimensional stability
  • Suitable for nitriding and flame hardening
  • High core strength with surface hardness after heat treatment

Typical Applications in Defence & Aerospace:
  • Aerospace gearboxes and shafts
  • Landing gear components
  • Missile motor casings
  • Crankshafts, propeller shafts, and heavy-duty gear parts
  • High-performance engine components

EN25 Steel


Standard: BS 970 (EN25)

Category: Nickel-Chromium-Molybdenum Alloy Steel

Overview: EN25 is a high-strength alloy steel with excellent fatigue resistance, toughness, and hardenability. It is widely used in defence and aerospace industries for critical components exposed to high stress and impact.


Chemical Composition (%):
Element Content
Carbon (C)0.35 – 0.45%
Silicon (Si)0.10 – 0.35%
Manganese (Mn)0.45 – 0.70%
Nickel (Ni)2.75 – 3.50%
Chromium (Cr)1.00 – 1.40%
Molybdenum (Mo)0.20 – 0.35%
Phosphorus (P)≤ 0.035%
Sulfur (S)≤ 0.035%
Mechanical Properties (Typical, Heat Treated):
  • Tensile Strength: 1000–1200 MPa
  • Yield Strength: 800–1000 MPa
  • Hardness: Up to 300–400 HB
  • Excellent fatigue resistance under cyclic loads

Key Properties:
  • High tensile and yield strength
  • Exceptional toughness and ductility
  • Good through-hardening response
  • Suitable for case hardening, nitriding, and flame hardening

Defence & Aerospace Applications:
  • Landing gear components
  • Aircraft shafts and structural parts
  • Missile and rocket motor casings
  • Heavy-duty military gears and drive shafts
  • Aerospace engine mounts and frames

EN26 Steel


Standard: BS 970 (EN26)

Category: High tensile nickel-chromium-molybdenum steel

Overview: EN26 is a very high-strength alloy steel offering outstanding toughness and fatigue resistance. It's suitable for components under high stress and dynamic loads in aerospace and defence applications.


Chemical Composition (%):
Element Content
Carbon (C)0.40 – 0.45%
Silicon (Si)0.10 – 0.35%
Manganese (Mn)0.45 – 0.70%
Nickel (Ni)2.75 – 3.50%
Chromium (Cr)1.00 – 1.40%
Molybdenum (Mo)0.45 – 0.65%
Phosphorus (P)≤ 0.035%
Sulfur (S)≤ 0.035%
Mechanical Properties (Typical, Heat Treated):
  • Tensile Strength: 1100–1400 MPa
  • Yield Strength: 900–1100 MPa
  • Hardness: Up to 400 HB
  • Excellent fatigue and impact resistance

Key Features:
  • Superior strength and toughness
  • Good hardenability and through-hardening
  • Suitable for nitriding and case hardening
  • High fatigue strength under cyclic stresses

Applications in Defence & Aerospace:
  • Aircraft landing gear and heavy-duty shafts
  • Missile and rocket structural parts
  • Military vehicle drive components
  • Aerospace engine supports and frames
  • Transmission and gear parts under extreme loads

EN30B Steel


Standard: BS 970 (EN30B)

Category: Nickel-Chromium-Molybdenum Alloy Steel

Overview: EN30B is a high-grade alloy steel offering excellent wear resistance, high core strength, and good impact properties, making it suitable for heavy-duty defence and aerospace applications.


Chemical Composition (%):
Element Content
Carbon (C)0.36 – 0.42%
Silicon (Si)0.10 – 0.35%
Manganese (Mn)0.45 – 0.70%
Nickel (Ni)3.00 – 3.75%
Chromium (Cr)1.00 – 1.40%
Molybdenum (Mo)0.45 – 0.65%
Phosphorus (P)≤ 0.035%
Sulfur (S)≤ 0.035%
Mechanical Properties (Typical, Heat Treated):
  • Tensile Strength: 1000–1300 MPa
  • Yield Strength: 800–1000 MPa
  • Hardness: Up to 400 HB (core); can exceed 60 HRC (surface)
  • Excellent wear and fatigue resistance

Key Features:
  • Exceptional core strength and toughness
  • Excellent surface hardness after case hardening
  • Good ductility and shock resistance
  • Highly wear-resistant and fatigue-resistant

Applications in Defence & Aerospace:
  • Aerospace gears and shafts
  • Rocket motor components and launch system parts
  • Military gear trains and drive systems
  • High-performance crankshafts and camshafts
  • Aircraft actuators and precision mechanisms

EN36 Steel


Standard: BS 970 (EN36 / EN36A)

Overview: EN36 is a low-carbon steel alloyed with nickel and chromium, primarily used in case hardening processes to provide a tough core with a very hard surface. It's ideal for heavy-duty components in aerospace and defence that need wear resistance and shock tolerance.


Chemical Composition (%):
Element Content
Carbon (C)0.10 – 0.16%
Silicon (Si)0.10 – 0.35%
Manganese (Mn)0.40 – 0.70%
Nickel (Ni)3.00 – 3.75%
Chromium (Cr)0.60 – 1.10%
Phosphorus (P)≤ 0.035%
Sulfur (S)≤ 0.035%
Key Properties:
  • Excellent case hardenability
  • Very hard, wear-resistant surface after treatment
  • Tough and shock-resistant core
  • High fatigue strength

Typical Applications:
  • Aerospace gears and shafts
  • Defence-grade camshafts and connecting rods
  • Automotive crankshafts and heavy-duty pinions
  • Industrial gears and splined shafts

EN47 Steel


Standard: BS 970 (EN47)

Overview: EN47 is a silicon-manganese alloyed spring steel known for its high fatigue strength, shock resistance, and durability. It is extensively used in the manufacture of heavy-duty springs in defence, aerospace, and railway applications.


Chemical Composition (%):
Element Content
Carbon (C)0.45 – 0.55%
Silicon (Si)1.50 – 2.00%
Manganese (Mn)0.50 – 0.90%
Chromium (Cr)≤ 0.35%
Phosphorus (P)≤ 0.05%
Sulfur (S)≤ 0.05%
Mechanical Properties (Typical, Heat Treated):
  • Tensile Strength: 850–1200 MPa
  • Yield Strength: 600–900 MPa
  • Hardness: 280–340 HB
  • Excellent fatigue and impact resistance

Key Features:
  • High resilience and elasticity
  • Excellent fatigue strength for cyclic loading
  • Good resistance to shock and deformation
  • Can be hardened and tempered for spring applications

Applications in Defence & Aerospace:
  • Helicopter suspension springs
  • Landing gear shock springs
  • Military vehicle suspension systems
  • Heavy-duty automotive and railway springs

EN52 Steel


Standard: BS 970 (EN52)

Overview: EN52 is a high-silicon, chromium-based steel grade specially developed for high-temperature environments like internal combustion engine valves. It offers excellent resistance to heat, corrosion, and wear, making it ideal for aerospace, defence, and automotive valve applications.


Chemical Composition (%):
Element Content
Carbon (C)0.50 – 0.60%
Silicon (Si)2.00 – 2.50%
Manganese (Mn)0.50 – 0.80%
Chromium (Cr)8.00 – 9.50%
Phosphorus (P)≤ 0.05%
Sulfur (S)≤ 0.05%
Mechanical Properties (Typical, Heat Treated):
  • Tensile Strength: 950–1150 MPa
  • Hardness: 280–340 HB
  • High resistance to scaling and oxidation at elevated temperatures
  • Excellent wear resistance

Key Features:
  • High-temperature strength and stability
  • Exceptional resistance to thermal fatigue
  • Corrosion and oxidation resistance under engine conditions
  • Ideal for use in extreme environments

Applications in Defence & Aerospace:
  • Aerospace engine intake and exhaust valves
  • High-performance defence vehicle engine valves
  • Automotive racing and heavy-duty engine components
  • Powerplant and turbo machinery valve systems

EN41B Steel


Standard: BS 970 (EN41B)

Overview: EN41B is a chromium-aluminium-molybdenum alloy steel designed for nitriding, offering outstanding surface hardness, wear resistance, and fatigue strength. It is widely used in aerospace and defence components that demand enhanced surface durability.


Chemical Composition (%):
Element Content
Carbon (C)0.35 – 0.45%
Silicon (Si)0.10 – 0.35%
Manganese (Mn)0.40 – 0.70%
Chromium (Cr)1.00 – 1.40%
Aluminium (Al)0.90 – 1.30%
Molybdenum (Mo)0.15 – 0.25%
Phosphorus (P)≤ 0.035%
Sulfur (S)≤ 0.035%
Mechanical Properties (Typical, After Nitriding):
  • Surface Hardness: up to 68 HRC
  • Tensile Strength (core): 700–950 MPa
  • Excellent wear resistance and fatigue strength
  • Good dimensional stability during heat treatment

Key Features:
  • Excellent nitriding response
  • High surface hardness with tough core
  • Long service life under wear and friction conditions
  • Good corrosion and oxidation resistance at elevated temperatures

Applications in Defence & Aerospace:
  • Aerospace actuator shafts and pins
  • Missile and launcher internal components
  • Defence-grade worm wheels and gear spindles
  • Tool holders, dies, and precision shafts

EN19 Steel


Standard: BS 970: 1955 (EN19), BS 970-3: 1991 (709M40)

Standard Specification:
  • BS 970: British Standard (EN19 / 709M40)
  • ASTM A29: Similar to 4140 grade (USA)
  • DIN: 42CrMo4 (Germany)
  • Werkstoff Number: 1.7225
  • Form Supplied: Round, Flat, Square Bars, Forgings
  • Delivery Condition: As Rolled, Annealed, or Hardened & Tempered

EN19 is a high tensile alloy steel with good ductility and shock resistance. It offers high fatigue strength, excellent wear resistance, and good machinability. It is widely used in aerospace and defence for critical mechanical parts subjected to dynamic loading.


Chemical Composition (%):
Element Content
Carbon (C)0.36 – 0.44%
Silicon (Si)0.10 – 0.35%
Manganese (Mn)0.60 – 0.90%
Chromium (Cr)0.90 – 1.50%
Molybdenum (Mo)0.15 – 0.35%
Sulfur (S)≤ 0.035%
Phosphorus (P)≤ 0.035%
Mechanical Properties (Typical, Heat Treated):
  • Tensile Strength: 850–1000 MPa
  • Yield Strength: 680 MPa
  • Hardness: 248–302 HB
  • Good toughness and impact resistance

Key Features:
  • High tensile strength with good wear resistance
  • Can be heat treated to achieve desired mechanical properties
  • Good fatigue and impact resistance
  • High machinability in annealed condition

Applications in Defence & Aerospace:
  • Aircraft landing gear components
  • Missile structural shafts and pins
  • Military vehicle drive shafts and axles
  • Gears, crankshafts, high-strength bolts

30CrNiMo8


Standard: DIN EN 10083 / Werkstoff 1.6580


Standard Specification:
  • DIN: 30CrNiMo8
  • Werkstoff Number: 1.6580
  • EN: EN 10083-3
  • ASTM Equivalent: AISI 4340 (approximate)
  • Form Supplied: Forged bars, Rolled bars, Flats, Discs
  • Delivery Condition: Annealed, Hardened & Tempered

30CrNiMo8 is a low-alloy steel known for high strength, toughness, and fatigue resistance. It performs excellently in dynamic, high-stress environments, making it ideal for aerospace and defence applications such as landing gear, rotor shafts, and high-load components.


Chemical Composition (%):
ElementContent
Carbon (C)0.26 – 0.34%
Silicon (Si)≤ 0.40%
Manganese (Mn)0.50 – 0.80%
Chromium (Cr)1.80 – 2.20%
Nickel (Ni)1.80 – 2.20%
Molybdenum (Mo)0.30 – 0.50%
Phosphorus (P)≤ 0.025%
Sulfur (S)≤ 0.035%
Mechanical Properties (Typical, Heat Treated):
  • Tensile Strength: 1000–1300 MPa
  • Yield Strength: ≥ 850 MPa
  • Elongation: ≥ 10%
  • Impact Strength: ≥ 35 J (at -20°C)
  • Hardness: 285–340 HB

Key Features:
  • High tensile strength and fatigue resistance
  • Excellent toughness, even at low temperatures
  • Good hardenability and wear resistance
  • Used in critical, highly stressed parts

Applications in Defence & Aerospace:
  • Aircraft structural and undercarriage parts
  • Missile and rotor shafts
  • Landing gear, spindles, and drive systems
  • Military vehicle drivetrain components

34CrNiMo6


Standard: EN 10083-3 / Werkstoff 1.6582

Standard Specification:
  • DIN: 34CrNiMo6
  • Werkstoff Number: 1.6582
  • EN: EN 10083-3
  • AISI Equivalent: 4340 (approximate)
  • Form Supplied: Rolled bars, Forged parts, Flats, Discs
  • Delivery Condition: Annealed or Quenched & Tempered

34CrNiMo6 is a high-strength, low-alloy steel known for its excellent toughness, fatigue strength, and good hardenability. It is widely used in defence and aerospace industries for components that undergo high dynamic stress and impact, such as rotor shafts, landing gear parts, crankshafts, and high-performance bolts.


9310


Standard Specification:
  • SAE: 9310
  • UNS: G93106
  • AMS: 6260, 6265, 6267
  • Form Supplied: Bars, Forgings, Tubes
  • Condition: Annealed, Normalized, Hardened & Tempered

SAE 9310 is a low-alloy, carburizing steel known for its outstanding core toughness, high case hardness, and excellent fatigue strength. It is widely used in aerospace, defence, and high-performance automotive applications where components are subjected to heavy wear and stress. Common parts made from 9310 include gears, shafts, pinions, and bearing races that require a hard surface and a strong, ductile core.


15CDV6


Standard Specification:
  • AFNOR: 15CDV6
  • EN Equivalent: 1.7734 / 15CrMoV6
  • Form Supplied: Bars, Tubes, Sheets
  • Delivery Condition: Annealed, Quenched & Tempered

15CDV6 is a low-alloy, high-strength steel with good weldability and excellent mechanical properties after heat treatment. It is widely used in aerospace, motorsport, and defence applications for manufacturing lightweight yet high-strength components such as suspension arms, roll cages, and structural tubing. It offers good toughness and fatigue resistance, making it suitable for dynamic and impact-loaded applications.


15CrMoV5-7


Standard Specification:
  • EN Standard: EN 10216-2 / EN 10028-2
  • Werkstoff Number: 1.7735
  • Grade Name: 15CrMoV5-7
  • Form Supplied: Seamless tubes, Plates, Forgings
  • Delivery Condition: Normalized and Tempered

15CrMoV5-7 is a chromium-molybdenum-vanadium alloy steel designed for use in high-temperature pressure vessels and steam systems. It offers excellent heat resistance, creep strength, and toughness at elevated temperatures. Commonly used in power plants, boilers, and petrochemical industries, it performs reliably in applications where long-term stability under high stress and heat is critical.


21CrMoV5-7


Standard Specification:
  • EN Standard: EN 10216-2 / EN 10028-2
  • Werkstoff Number: 1.7709
  • Grade Name: 21CrMoV5-7
  • Form Supplied: Seamless pipes, Forgings, Bars
  • Delivery Condition: Normalized and Tempered

21CrMoV5-7 is a chromium-molybdenum-vanadium alloy steel used in high-temperature applications such as pressure vessels, steam piping, and power generation components. It offers excellent creep resistance, high-temperature strength, and toughness. This steel grade is especially suitable for environments where sustained mechanical stress and elevated temperatures are present over long operating periods, such as in thermal power plants and refineries.


X22CrMoV12-1


Standard Specification:
  • EN Standard: EN 10028-2 / EN 10216-2
  • Werkstoff Number: 1.4923
  • Grade Name: X22CrMoV12-1
  • Form Supplied: Bars, Tubes, Plates, Forgings
  • Delivery Condition: Solution annealed and tempered

X22CrMoV12-1 is a high-performance martensitic stainless steel alloyed with chromium, molybdenum, and vanadium. It exhibits excellent resistance to heat and oxidation, high creep strength, and good corrosion resistance in steam and turbine environments. This grade is widely used in the construction of power plant components such as steam turbine blades, high-pressure boiler tubes, and rotors that operate at elevated temperatures and under high mechanical loads.


1.4923


Standard Specification:
  • EN Designation: X22CrMoV12-1
  • Werkstoff Number: 1.4923
  • Standards: EN 10028-2, EN 10216-2
  • Form Supplied: Forgings, Bars, Tubes, Plates
  • Delivery Condition: Solution annealed and tempered

1.4923 (X22CrMoV12-1) is a martensitic stainless steel that combines high strength with good corrosion and oxidation resistance at elevated temperatures. It is widely used in the energy and power industries for parts like steam turbine blades, pressure vessels, and boiler tubes. Its chemical composition includes chromium, molybdenum, and vanadium, providing excellent creep resistance and structural stability.


17-4 PH Stainless Steel


17-4 PH (Precipitation Hardening) stainless steel, also known as UNS S17400 or Type 630, is a martensitic stainless steel known for:

  • High strength
  • Good corrosion resistance
  • Excellent mechanical properties up to 600°F (316°C)
  • Versatile heat treatment options for varying strength and toughness

It is widely used in aerospace, defense, and high-performance engineering components such as aircraft parts, missile components, and reactor parts.

Standard Specifications
Specification Details
UNS Number S17400
ASTM Standards A564 (bars), A705 (forgings), A693 (sheets/plates)
AMS Specifications AMS 5643 (bars & forgings), AMS 5604 (sheet & strip)
Typical Composition Cr: 15–17.5%, Ni: 3–5%, Cu: 3–5%, Nb/Ta: 0.15–0.45%, Fe: Balance
Heat Treatment H900, H1025, H1150 (varies mechanical properties)

15-5 PH Stainless Steel

15-5 PH (Precipitation Hardening) stainless steel is a martensitic, chromium-nickel-copper steel that offers:

  • High strength and hardness
  • Excellent corrosion resistance
  • Good mechanical properties in both annealed and heat-treated conditions
  • Better transverse toughness than 17-4 PH due to its refined microstructure

It is widely used in aerospace, defense, petrochemical, and other high-performance industries requiring strength and corrosion resistance.

Standard Specifications
Specification Details
UNS Number S15500
ASTM Standards A564 (bars), A705 (forgings), A693 (plates)
AMS Specifications AMS 5659 (bars & forgings), AMS 5862 (plates)
Typical Composition Cr: 14–15.5%, Ni: 3.5–5.5%, Cu: 2.5–4.5%, Nb: 0.15–0.45%, Fe: Balance
Heat Treatment H900 to H1150, providing varying strength and ductility

X4CrNiMo15-5-1 Stainless Steel


X4CrNiMo15-5-1 is the European designation (EN 1.4545) for the precipitation-hardening stainless steel known internationally as 15-5 PH. This martensitic steel is known for:

  • High mechanical strength and hardness
  • Excellent corrosion resistance, especially in marine and aerospace environments
  • Good weldability and machinability
  • Stable mechanical properties after heat treatment

Commonly used in aerospace, defense, marine, and chemical industries for high-strength, corrosion-resistant components.

Standard Specifications
Specification Details
EN Number 1.4545
UNS Equivalent S15500 (15-5 PH)
Standard EN 10088-3 (stainless steels for general purposes)
Chemical Composition Cr: 14–15.5%, Ni: 3.5–5.5%, Cu: 2.5–4.5%, Mo: 0.2–0.6%, Nb: 0.15–0.45%, Fe: Balance
Heat Treatment Solution treated and aged (e.g. H900 to H1150)

F6NM Stainless Steel

F6NM is a modified martensitic stainless steel (EN 1.4313 / X3CrNiMo13-4) with added nickel and molybdenum to improve toughness and corrosion resistance. It is commonly used in:

  • Defense and naval components
  • Hydroelectric turbine parts
  • Aerospace landing gear and structural parts
  • Pressure-containing parts in harsh environments

It combines moderate corrosion resistance with good mechanical strength and weldability after proper heat treatment.

Standard Specifications
Specification Details
EN Number 1.4313
UNS Equivalent S41500 (similar)
Steel Name X3CrNiMo13-4
Standards EN 10088-3, ASTM A182 (forgings), ASTM A743 (castings)
Chemical Composition Cr: 12–14%, Ni: 3.5–4.5%, Mo: 0.3–0.7%, C: ≤0.03%, Fe: Balance
Heat Treatment Solution annealed and tempered (typically around 620–670°C)

AISI 415 Stainless Steel

AISI 415 is a martensitic stainless steel that contains added nickel to enhance its toughness over AISI 410. It offers:

  • Good corrosion resistance
  • High strength and hardness after heat treatment
  • Improved impact toughness due to nickel addition
  • Good wear resistance, especially in hardened condition

It is commonly used in aerospace and defense applications like structural parts, shafts, fasteners, and components requiring strength and moderate corrosion resistance.

Standard Specifications
Specification Details
AISI/SAE 415
UNS Number S41500
Standards ASTM A276 (bars), ASTM A182 (forgings), ASTM A479 (engineering applications)
Chemical Composition Cr: 11.5–13.5%, Ni: 1.5–2.5%, Mn: ≤1.0%, C: 0.05–0.15%, Fe: Balance
Heat Treatment Quenched and tempered to enhance strength and toughness

1.4313 Stainless Steel (X3CrNiMo13-4)

1.4313 stainless steel, also known as X3CrNiMo13-4, is a low-carbon, martensitic stainless steel offering a good balance of strength, toughness, and corrosion resistance. It is especially valued in:

  • Defense components like naval shafts and structural parts
  • Hydroelectric and energy sector equipment
  • Aerospace structural applications
  • Heavy-duty mechanical engineering

Its weldability and mechanical performance make it a common choice for demanding environments with moderate corrosion exposure.

Standard Specifications
Specification Details
EN Number 1.4313
Steel Name X3CrNiMo13-4
Standards EN 10088-3, ASTM A182, ASTM A743
Chemical Composition Cr: 12.5–14.5%, Ni: 3.5–4.5%, Mo: 0.3–0.7%, C: ≤0.03%, Mn: ≤1%, Si: ≤0.5%, Fe: Balance
Heat Treatment Solution annealed and tempered (around 620–670°C for desired properties)

AISI 422 Stainless Steel

AISI 422 is a hardenable martensitic stainless steel known for its high strength, excellent oxidation resistance, and good scaling resistance at elevated temperatures. It is primarily used in:

  • Aerospace turbine components and compressor parts
  • High-temperature structural applications
  • Defense components requiring high mechanical strength
  • Steam turbine buckets, blades, and valves

This grade retains strength and toughness at elevated temperatures up to 649°C (1200°F), making it suitable for demanding aerospace environments.

Standard Specifications
Specification Details
AISI/SAE 422
UNS Number S42200
Standards ASTM A565 (forgings), AMS 5655, AMS 5622
Chemical Composition Cr: 11.0–13.0%, Ni: 0.5–1.0%, Mo: 0.75–1.25%, W: 0.75–1.25%, V: 0.20–0.35%, C: 0.20–0.25%, Fe: Balance
Heat Treatment Austenitized, quenched, and tempered for high strength and heat resistance

B4B Boron Steel

B4B is a **low-carbon boron-alloyed steel**, enhanced for hardenability and strength through heat treatment. It is commonly used in:

  • Defense structural components
  • Automotive and armored vehicle parts
  • High-strength reinforcement and welded structures
  • Wear-resistant tools and agricultural parts

Its low carbon content offers good weldability, while boron addition significantly improves hardenability after quenching.

Standard Specifications
Specification Details
Steel Grade B4B (EN 10027)
Steel Type Low-carbon boron steel
Typical Applications Defense, structural, automotive, agricultural tools
Chemical Composition C: ≤ 0.08%, Mn: 0.30–0.60%, Si: ≤ 0.30%, B: ~0.001–0.005%, Fe: Balance
Standards EN 10083-3, EN 10263-4 (hot forging), ISO 683
Heat Treatment Can be quenched and tempered for high hardness and strength

AISI 616 HT Stainless Steel


AISI 616 HT is a **high-temperature martensitic stainless steel**, often used in turbine engine parts, aerospace fasteners, and components requiring strength, creep resistance, and corrosion resistance at elevated temperatures. It features:

  • Good high-temperature strength and oxidation resistance
  • Martensitic microstructure with precipitation hardening capability
  • Used in gas turbines, exhausts, and structural aerospace applications
  • Good dimensional stability at high operating temperatures

It is typically used in a heat-treated (HT) condition to achieve the best mechanical properties for service in extreme environments.

Standard Specifications
Specification Details
Grade AISI 616 HT
UNS Custom grades; varies by manufacturer (related to S17400 or similar)
Typical Standards AMS 5931, proprietary specs (aerospace-specific)
Chemical Composition Cr: ~14–16%, Ni: ~4–6%, Mo: ~1–2%, C: ≤ 0.03%, Cu/Nb/B: as needed for hardenability, Fe: Balance
Heat Treatment Solution annealed, air cooled, followed by aging or precipitation hardening

AISI 615 HT Stainless Steel


AISI 615 HT is a **high-temperature resistant martensitic stainless steel** often used in aerospace turbine engine parts, fasteners, and critical structural applications. Its properties make it well-suited for:

  • Gas turbine and exhaust components
  • Defense applications involving sustained thermal loads
  • Aircraft engine hardware requiring high strength and creep resistance
  • Environments needing both corrosion resistance and heat resistance

The "HT" designation refers to its heat-treated condition, which enhances mechanical and thermal performance.

Standard Specifications
Specification Details
Grade AISI 615 HT
Type High-strength martensitic stainless steel (heat treated)
Typical Applications Turbine engines, aerospace fasteners, exhaust systems
Chemical Composition Cr: ~14–15%, Ni: ~3–5%, Mo: ~1–2%, C: ≤ 0.05%, B/Nb/V additions (as required), Fe: Balance
Standards AMS 5930 (or similar), Aerospace-specific proprietary specs
Heat Treatment Solution annealed and aged (precipitation hardened) for optimal high-temperature strength

AISI 418 Stainless Steel

AISI 418 is a **hardenable martensitic stainless steel** known for its high mechanical strength, corrosion resistance, and good performance at elevated temperatures. It is commonly used in:

  • Aerospace and turbine engine components
  • Defense parts requiring strength and wear resistance
  • Steam turbine blades and bolting applications
  • Heat-resistant structural hardware

Its combination of strength, toughness, and oxidation resistance makes it ideal for thermal and mechanical stress environments.

Standard Specifications
Specification Details
Grade AISI 418
UNS S41800
Type Martensitic stainless steel
Typical Standards ASTM A565, AMS 5616
Chemical Composition Cr: 12.0–14.0%, Ni: 2.5–3.5%, Mo: ~1.0%, V: ~0.3%, C: 0.15–0.25%, Fe: Balance
Heat Treatment Quenched and tempered to achieve high strength and toughness

EN57 Stainless Steel

EN57 is a **ferritic stainless steel** characterized by good corrosion resistance, magnetic properties, and excellent cold-forming capabilities. Though not typically used in high-stress aerospace parts, it finds utility in:

  • Defense housings and covers in non-critical zones
  • Household appliances and utensils
  • Automotive trims and exhaust parts
  • Decorative applications and architectural fittings

It is suitable for moderately corrosive environments and valued for its ease of fabrication and affordability.

Standard Specifications
Specification Details
Steel Grade EN57 (similar to AISI 430)
Type Ferritic stainless steel
Chemical Composition Cr: 16.0–18.0%, C: ≤ 0.12%, Ni: ≤ 0.5%, Fe: Balance
UNS Equivalent S43000
Standards BS 970, EN 10088-2, ASTM A240
Applications Low-load defense parts, kitchenware, decorative trim, panels

AISI 431 Stainless Steel

AISI 431 is a **martensitic stainless steel** offering a combination of **high strength**, **good toughness**, and **moderate corrosion resistance**. It is commonly used in aerospace and defense industries for components requiring:

  • High tensile strength and hardness
  • Good resistance to fatigue and stress corrosion cracking
  • Wear resistance in mildly corrosive environments
  • Applications such as aircraft fittings, shafts, and fasteners

It can be hardened through heat treatment and has better corrosion resistance than other martensitic grades like AISI 410.

Standard Specifications
Specification Details
Grade AISI 431
UNS S43100
Type Martensitic stainless steel
Chemical Composition Cr: 15.0–17.0%, Ni: 1.25–2.50%, C: ≤ 0.20%, Mn, Si, P, S: trace, Fe: Balance
Standards ASTM A276, A314, A479, AMS 5628
Heat Treatment Hardened by quenching and tempering to achieve high strength

1.4057 Stainless Steel (X17CrNi16-2)

1.4057 (X17CrNi16-2) is a **hardenable martensitic stainless steel** that offers a combination of **high mechanical strength** and **moderate corrosion resistance**. It is similar to AISI 431 and is commonly used in:

  • Defense and aerospace components exposed to wear and stress
  • Hydraulic parts and turbine blades
  • Shafts, bolts, valves, and fasteners requiring strength and corrosion resistance
  • Marine and offshore applications

Thanks to its chromium and nickel content, it has improved corrosion resistance over lower-grade martensitic steels.

Standard Specifications
Specification Details
Steel Grade 1.4057 / X17CrNi16-2
Type Martensitic stainless steel (hardenable)
Equivalent AISI 431, UNS S43100
Chemical Composition Cr: 15.5–17.5%, Ni: 1.5–2.5%, C: ≤ 0.17%, Mn, Si: ≤ 1%, Fe: Balance
Standards EN 10088-3, DIN 17440, ASTM A276
Heat Treatment Quenched and tempered to achieve high tensile strength and wear resistance

EN40B Steel


EN40B is a high-strength, low-alloy steel primarily used in the defense and aerospace sectors for components that require a balance between strength and weight. This material is widely favored for its excellent mechanical properties, making it suitable for parts that will be subjected to high stress and extreme conditions.


1. Composition

EN40B steel contains the following primary elements:

  • Chromium (Cr) – Improves hardenability, corrosion resistance, and strength.
  • Molybdenum (Mo) – Enhances wear resistance and toughness.
  • Carbon (C) – Provides hardness and strength after heat treatment.
  • Nickel (Ni) – Increases toughness and resistance to impact.

2. Mechanical Properties

EN40B steel is engineered to deliver optimal strength while maintaining a good level of toughness. Below are the typical mechanical properties:

Property Value
Tensile Strength 750-1000 MPa
Yield Strength 450-800 MPa
Elongation 10-15%
Hardness (Brinell) 200-250 HB
Impact Toughness ≥ 40 J at -20°C
3. Heat Treatment

EN40B responds very well to heat treatment, making it versatile in different manufacturing processes:

  • Annealing: 850-900°C followed by slow cooling.
  • Quenching: 850-900°C followed by water or oil quenching.
  • Tempering: 450-600°C to adjust hardness and increase toughness.

These heat treatments allow the material to be tailored for specific applications, balancing hardness and toughness according to the needs of the component.


4. Applications in Defense & Aerospace

EN40B is widely used in various high-performance applications, especially in industries where reliability and strength are paramount. Some notable uses in defense and aerospace include:

  • Gears and Shafts: Used in high-stress applications such as landing gear mechanisms, gearbox components, and missile systems.
  • Landing Gear Parts: The high toughness and impact resistance of EN40B make it ideal for use in aircraft landing gear and associated components.
  • Engine Parts: EN40B is used for components that are subject to high operational loads, including shafts, axles, and crankshafts.
  • Missile Components: EN40B is also used in missile components, where strength and durability under extreme conditions are critical.

5. Standards & Specifications

For applications in defense and aerospace, EN40B steel must adhere to stringent standards to ensure reliability and performance under demanding conditions. Some of the relevant standards include:

  • MIL-STD-461: Ensures electromagnetic compatibility in military equipment.
  • MIL-STD-810: Specifies environmental testing for military hardware, including exposure to temperature extremes, humidity, and vibration.
  • Aerospace Material Specifications: Aerospace-grade EN40B components must meet specific requirements laid out by organizations like ASTM and the FAA for parts that meet aviation safety standards.

EN40B steel is a versatile and reliable material for defense and aerospace industries due to its excellent mechanical properties, especially in high-stress applications. Its ability to withstand harsh environments while maintaining strength and toughness makes it a go-to choice for various critical components. However, for each specific application, it is recommended to consult with engineers and materials scientists to ensure optimal selection and performance of the material.