15CDV6, 14CrMoV6-9, 1.7734, 1.7735, 1.8521

Aerospace steels 15CDV6, 14CrMoV6-9, 1.7734, 1.7735, and 1.8521, including chemical composition, mechanical properties, heat treatment, and applications per AIR 9160/C.

15CDV6, 14CrMoV6-9, 1.7734, 1.7735, 1.8521

What is 15CDV6, 14CrMoV6-9, 1.7734, 1.7735, 1.8521?

Aerospace and aviation industries demand high-performance steels capable of withstanding extreme mechanical stresses, high temperatures, and corrosive environments. Key alloys such as 15CDV6, 14CrMoV6-9, 1.7734 (FE-PL52S), 1.7735, and 1.8521 (15CrMoV5-9) are widely used in critical components like turbine parts, landing gear, and structural elements.

This guide provides a detailed comparison of these steels, covering:

  • Chemical compositions
  • Mechanical properties (tensile strength, yield strength, elongation)
  • Heat treatment processes (annealing, quenching & tempering)
  • High-temperature performance (creep resistance, stress rupture)
  • Welding & machining characteristics
  • Equivalent materials

These high-strength, creep-resistant steels are essential in aerospace and aviation for critical high-stress, high-temperature applications. Understanding their composition, heat treatment, and mechanical behavior ensures optimal performance in demanding environments.

For material selection, processing, or welding recommendations, consult the relevant AIR 9160/C, DIN, or EN standards for precise specifications.

References:

  • AIR 9160/C Aerospace Material Standards
  • DIN EN 10028 (Pressure Vessel Steels)
  • ASM Aerospace Materials Handbook

Applications

Steel Grade Standard Designation Key Applications
15CDV6 AIR 9160/C Aircraft landing gear, high-stress structural parts
14CrMoV6-9 1.7735 High-temperature turbine components, pressure vessels
1.7734 (FE-PL52S) 12CrMoV6-9 Boiler tubes, heat exchangers, aerospace piping
1.8521 (15CrMoV5-9) DIN 1.8521 Jet engine components, fasteners, high-load bolts
15CrMoV5-10 (1.7745) DIN 1.7745 Exhaust systems, turbine casings

Practical Implications for Aerospace Applications

Thermal Management:

  • 14CrMoV6-9 & 1.7734 (lower conductivity) are better for thermal insulation (e.g., turbine shrouds).
  • 15CDV6 (higher conductivity) suits heat exchangers & cooling systems.

Dimensional Stability:

  • 1.7734 has the lowest thermal expansion, ideal for precision components.

Weight Considerations:

  • All steels have similar densities (~7.85-7.87 g/cm³), making them comparable in weight-critical designs.

Stiffness at High Temperatures:

  • 15CDV6 & 1.8521 retain stiffness best at 500-600°C, useful for engine mounts & load-bearing structures.

Chemical Composition (%)

Element

15CDV6, AIR 9160

14CrMoV6-9, 1.7735

12CrMoV6-9, 1.7734

15CrMoV5-9, 1.8521

15CrMoV5-10, 1.7745
C 0.12-0.18 0.10-0.15 0.08-0.15 0.12-0.18 0.12-0.18
Si ≤0.40 ≤0.50 ≤0.50 ≤0.40 ≤0.40
Mn 0.40-0.70 0.40-0.70 0.40-0.70 0.40-0.70 0.40-0.70
Cr 0.90-1.20 1.80-2.20 1.80-2.20 1.00-1.30 1.00-1.30
Mo 0.50-0.70 0.90-1.10 0.90-1.10 0.90-1.10 0.90-1.10
V 0.15-0.25 0.25-0.35 0.25-0.35 0.25-0.35 0.25-0.35
P (max) 0.025 0.025 0.025 0.025 0.025
S (max) 0.025 0.025 0.025 0.025 0.025

Material Properties

Room Temperature Properties

Grade Condition Tensile (MPa) Yield (MPa) Elongation (%) Hardness (HB)
15CDV6 +QT (Quenched & Tempered) 850-1050 ≥700 ≥12 248-302
14CrMoV6-9 (1.7735) +HT (Heat Treated) 650-850 ≥450 ≥16 200-250
1.7734 (12CrMoV6-9) +A (Annealed) 550-750 ≥350 ≥18 180-220
1.8521 (15CrMoV5-9) +QT 900-1100 ≥750 ≥10 270-330
1.7745 (15CrMoV5-10) +QT 950-1150 ≥800 ≥9 280-340

High-Temperature Properties

These steels retain strength at elevated temperatures (up to 600°C), making them ideal for jet engines and exhaust systems.

Grade Temperature (°C) Creep Strength (MPa/10,000h) Rupture Strength (MPa/100h)
15CDV6 500 250 450
14CrMoV6-9 550 180 380
1.7734 550 160 350
1.8521 600 200 420
1.7745 600 220 450

Physical Properties

Physical properties such as density, thermal expansion, thermal conductivity, and electrical resistivity are crucial for material selection in aerospace and aviation applications.

Physical properties such as density, thermal expansion, thermal conductivity, and electrical resistivity are crucial for material selection in aerospace and aviation applications.

Density (g/cm³)

Density affects weight-critical aerospace components.

Grade Density (g/cm³)
15CDV6 7.85
14CrMoV6-9 (1.7735) 7.87
1.7734 (12CrMoV6-9) 7.86
1.8521 (15CrMoV5-9) 7.85
1.7745 (15CrMoV5-10) 7.86

Note: All values are near 7.85-7.87 g/cm³, typical for low-alloy steels.

Thermal Expansion Coefficient (10⁻⁶/°C)

Thermal expansion impacts dimensional stability under temperature fluctuations.

Grade 20-100°C 20-300°C 20-500°C 20-600°C
15CDV6 11.5 12.2 13.0 13.5
14CrMoV6-9 11.2 11.8 12.6 13.1
1.7734 11.0 11.6 12.4 12.9
1.8521 11.3 12.0 12.8 13.3
1.7745 11.4 12.1 12.9 13.4

Key Takeaway:

  • Higher Cr-Mo-V content slightly reduces thermal expansion.
  • Critical for turbine blades, exhaust systems, and high-temperature structures.

Thermal Conductivity (W/m·K)

Thermal conductivity determines heat dissipation efficiency.

Grade 20°C 200°C 400°C 600°C
15CDV6 42 40 38 36
14CrMoV6-9 38 36 34 32
1.7734 37 35 33 31
1.8521 40 38 36 34
1.7745 39 37 35 33

Key Takeaway:

  • Lower thermal conductivity in high-Cr-Mo steels (better for thermal barrier applications).
  • 15CDV6 has the highest conductivity, suitable for heat exchangers.

Electrical Resistivity (μΩ·m)

Important for electromagnetic and grounding applications.

Grade Resistivity (μΩ·m) at 20°C
15CDV6 0.22
14CrMoV6-9 0.25
1.7734 0.24
1.8521 0.23
1.7745 0.24

Key Takeaway:

  • Higher alloying (Cr, Mo, V) increases resistivity.
  • Still low enough for most aerospace electrical applications.

Specific Heat Capacity (J/kg·K)

Determines heat absorption capability.

Grade 20°C 300°C 500°C
15CDV6 460 520 580
14CrMoV6-9 470 530 590
1.7734 465 525 585
1.8521 475 535 595
1.7745 480 540 600

Key Takeaway:

  • Increases with temperature due to lattice vibrations.
  • Higher Cr-Mo steels absorb slightly more heat.

Elastic Modulus (Young's Modulus, GPa)

Stiffness under load.

Grade 20°C 300°C 500°C 600°C
15CDV6 210 195 180 170
14CrMoV6-9 205 190 175 165
1.7734 200 185 170 160
1.8521 208 193 178 168
1.7745 207 192 177 167

Key Takeaway:

  • Decreases with temperature (critical for high-temperature structural design).
  • 15CDV6 retains the highest stiffness at elevated temperatures.

Magnetic Properties

  • All grades are ferromagnetic (attracted to magnets).
  • Magnetic permeability decreases slightly at high temperatures.

Summary of Key Physical Properties

Property 15CDV6 14CrMoV6-9 1.7734 1.8521 1.7745
Density (g/cm³) 7.85 7.87 7.86 7.85 7.86
Thermal Expansion (10⁻⁶/°C, 20-600°C) 13.5 13.1 12.9 13.3 13.4
Thermal Conductivity (W/m·K, 20°C) 42 38 37 40 39
Electrical Resistivity (μΩ·m) 0.22 0.25 0.24 0.23 0.24
Young's Modulus (GPa, 20°C) 210 205 200 208 207

Heat Treatment

Grade Annealing (°C) Quenching (°C) Tempering (°C) Recommended Condition
15CDV6 850-900 920-950 (Oil) 600-650 +QT (Quenched & Tempered)
14CrMoV6-9 880-920 950-980 (Air/Oil) 650-700 +HT (Heat Treated)
1.7734 860-900 920-950 (Air) 620-680 +A (Annealed)
1.8521 870-910 930-970 (Oil) 600-650 +QT
1.7745 880-920 940-980 (Oil) 620-670 +QT

Processing Performance

  • Machinability: Moderate (similar to low-alloy steels, requires carbide tools).
  • Weldability: Preheating (200-300°C) and post-weld heat treatment (PWHT) recommended to avoid cracking.
  • Formability: Good in annealed condition, but high strength in +QT state limits cold forming.

Equivalent Materials & Cross-References

Grade EN/DIN UNS AISI/SAE Similar Grades
15CDV6 - - - AISI 6150 (modified)
14CrMoV6-9 1.7735 - - 14MoV6-3 (DIN)
1.7734 12CrMoV6-9 - - 13CrMo4-5 (similar)
1.8521 15CrMoV5-9 - - 15CrMoV5-10 (DIN)
1.7745 15CrMoV5-10 - - 14CrMoV6-9 (similar)
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