If you work in industries like automotive, aerospace, or heavy machinery, you need steel that balances a hard, wear-resistant surface with a tough core. EN 18NiCrMo14-6 case hardening steel—a European-standard alloy rich in nickel, chromium, and molybdenum—delivers exactly that. This guide breaks down its key properties, real-world applications, manufacturing process, and how it compares to other materials, helping you choose the right steel for high-stress, wear-prone parts.
1. Material Properties of EN 18NiCrMo14-6 Case Hardening Steel
EN 18NiCrMo14-6’s unique alloy composition (especially high nickel and molybdenum) makes it ideal for case hardening. Let’s explore its properties in detail.
1.1 Chemical Composition
EN 18NiCrMo14-6 follows strict European standards (EN 10084), ensuring consistent performance for case hardening. Below is its typical chemical makeup:
| Element | Symbol | Content Range (%) | Key Role |
|---|---|---|---|
| Carbon (C) | C | 0.15 – 0.21 | Low enough for ductile core; reacts with carburizing to form hard surface |
| Nickel (Ni) | Ni | 3.00 – 3.50 | Boosts core toughness and fatigue resistance |
| Chromium (Cr) | Cr | 1.40 – 1.70 | Improves hardenability and surface wear resistance |
| Molybdenum (Mo) | Mo | 0.45 – 0.55 | Enhances high-temperature strength and prevents temper brittleness |
| Manganese (Mn) | Mn | 0.50 – 0.80 | Increases workability and tensile strength |
| Silicon (Si) | Si | 0.15 – 0.35 | Aids deoxidation during steelmaking |
| Sulfur (S) | S | ≤ 0.035 | Controlled to avoid brittleness |
| Phosphorus (P) | P | ≤ 0.035 | Minimized to prevent cracking |
| Copper (Cu) | Cu | ≤ 0.30 | Trace element with no major performance impact |
1.2 Physical Properties
These properties describe how EN 18NiCrMo14-6 behaves under physical conditions like temperature and magnetism:
- Density: 7.85 g/cm³ (same as most nickel-chromium-molybdenum steels)
- Melting Point: 1,420 – 1,460 °C (2,588 – 2,660 °F)
- Thermal Conductivity: 44.0 W/(m·K) at 20 °C (room temperature)
- Coefficient of Thermal Expansion: 11.8 × 10⁻⁶/°C (from 20 – 100 °C)
- Magnetic Properties: Ferromagnetic (attracts magnets), useful for sorting and non-destructive testing.
1.3 Mechanical Properties
Mechanical properties of EN 18NiCrMo14-6 depend on case hardening (carburizing + quenching + tempering). Below are typical values for the surface (case) and core:
| Property | Measurement Method | Surface (Case) Value | Core Value |
|---|---|---|---|
| Hardness (Rockwell) | HRC | 58 – 62 HRC | 30 – 35 HRC |
| Hardness (Vickers) | HV | 550 – 600 HV | 280 – 320 HV |
| Tensile Strength | MPa | — | ≥ 900 MPa |
| Yield Strength | MPa | — | ≥ 650 MPa |
| Elongation | % (in 50 mm) | — | ≥ 15% |
| Impact Toughness | J (at 20 °C) | — | ≥ 60 J |
| Fatigue Limit | MPa (rotating beam) | — | ≥ 450 MPa |
1.4 Other Properties
EN 18NiCrMo14-6’s standout properties make it perfect for case-hardened parts:
- Case Hardening Depth: Typically 0.8 – 2.0 mm (adjustable via carburizing time/temperature) — enough for wear-prone surfaces like gear teeth.
- Wear Resistance: Hard surface (from carburizing) resists abrasion, while the tough core absorbs impact.
- Fatigue Resistance: Nickel and molybdenum improve resistance to repeated loads—critical for gears and shafts.
- Hardenability: Excellent—can be case-hardened evenly across large or complex parts (e.g., axles).
- Corrosion Resistance: Moderate (better than standard carbon steels); needs coatings (like zinc plating) for wet/harsh environments.
- Core Hardness: Balanced toughness (30 – 35 HRC) prevents parts from breaking under impact.
2. Applications of EN 18NiCrMo14-6 Case Hardening Steel
EN 18NiCrMo14-6’s hard surface and tough core make it ideal for parts that face both wear and impact. Here are its key uses:
- Gears: The #1 application—including automotive transmission gears, industrial gearbox gears, and aerospace engine gears (where wear and torque meet).
- Shafts: Drive shafts in trucks, industrial machinery, and turbines (needing a hard outer layer to resist wear and a tough core to handle torque).
- Axles: Automotive axles (especially heavy-duty trucks) and agricultural machinery axles—absorbing impact while resisting wear.
- Pinions: Small gears in gearboxes or steering systems (relying on precise case hardening for smooth operation).
- Automotive Components: Clutch hubs, camshafts, and differential parts—high-stress parts needing wear resistance.
- Industrial Machinery: Conveyor drive gears, pump shafts, and compressor components—operating under long hours and heavy loads.
- Aerospace Components: Landing gear shafts and engine accessory gears (where reliability and weight balance matter).
- Agricultural Machinery: Tractor gearboxes and harvester shafts—handling dusty, high-impact conditions.
- Mining Equipment: Crusher gears and conveyor shafts—resisting abrasion from rocks and heavy loads.
3. Manufacturing Techniques for EN 18NiCrMo14-6
Producing EN 18NiCrMo14-6 requires precise steps to achieve the perfect case-hardened finish. Here’s the typical process:
- Steelmaking:
- Most EN 18NiCrMo14-6 is made using an Electric Arc Furnace (EAF) with vacuum degassing. This removes impurities and ensures precise control of alloy elements (especially nickel and molybdenum) to meet EN 10084 standards.
- Rolling:
- After steelmaking, the metal is Hot Rolled (at 1,150 – 1,250 °C) into billets, bars, or sheets. For precision parts, it’s then Cold Rolled (room temperature) to improve surface finish and dimensional accuracy.
- Precision Forging:
- Complex parts (like gears or shafts) are forged into near-final shapes at high temperatures. This refines the grain structure, enhancing core toughness—critical for high-stress applications.
- Machining (Pre-Carburizing):
- Forged parts are machined to near-final dimensions using Turning (for cylindrical shapes like shafts) or Milling (for gears). A small tolerance (0.1 – 0.2 mm) is left for post-heat treatment grinding.
- Heat Treatment (Case Hardening):
- The most critical step—creating a hard surface and tough core:
- Carburizing: Heat the part to 880 – 930 °C in a carbon-rich atmosphere (natural gas or propane) for 4 – 12 hours. Carbon diffuses into the surface (0.8 – 2.0 mm deep) to raise carbon content to 0.8 – 1.0%.
- Quenching: Rapidly cool the part in oil or high-pressure gas to harden the carbon-rich surface.
- Tempering: Reheat to 180 – 220 °C to reduce brittleness while maintaining surface hardness.
- The most critical step—creating a hard surface and tough core:
- Machining (Post-Carburizing):
- Parts are Ground to final dimensions (removing the small pre-carburizing tolerance). This ensures ultra-smooth surfaces (critical for gear teeth) and tight tolerances (±0.005 mm).
- Surface Treatment:
- Optional steps to enhance performance:
- Nitriding: Adds a thin, extra-hard layer (if even higher wear resistance is needed).
- Blackening: Forms a protective oxide layer to prevent minor rust.
- Coating: Zinc plating or powder coating for corrosion resistance in wet environments.
- Optional steps to enhance performance:
- Quality Control:
- Rigorous testing ensures quality:
- Chemical analysis: Verify alloy content via spectrometry.
- Case hardening depth test: Measure surface carbon penetration (using microhardness testing).
- Hardness testing: Check surface (HRC) and core (HRC) hardness.
- Non-destructive testing: Ultrasonic testing for internal cracks; magnetic particle testing for surface defects.
- Dimensional inspection: Use CMMs (Coordinate Measuring Machines) to check tolerances.
- Rigorous testing ensures quality:
4. Case Studies: EN 18NiCrMo14-6 in Action
Real-world examples show how EN 18NiCrMo14-6 solves industry challenges.
Case Study 1: Automotive Gear Failure Analysis
A heavy-duty truck manufacturer faced frequent gear failures in their transmission (lasting only 150,000 km). The original gears used a low-nickel case hardening steel, which had a brittle core and uneven case depth. Switching to EN 18NiCrMo14-6 gears (with controlled carburizing to 1.2 mm case depth) extended gear life to 400,000 km. This reduced warranty claims by 80% and saved $500,000 annually.
Case Study 2: Mining Equipment Pinion Optimization
A mining company struggled with pinion failures in their crusher (every 3 months) due to abrasion and impact. They replaced the existing steel with EN 18NiCrMo14-6 pinions, paired with nitriding surface treatment. Post-switch, pinion life increased to 12 months, cutting maintenance downtime by 75% and replacement costs by 60%.
5. EN 18NiCrMo14-6 vs. Other Materials
How does EN 18NiCrMo14-6 compare to other case hardening steels and materials? The table below breaks it down:
| Material | Similarities to EN 18NiCrMo14-6 | Key Differences | Best For |
|---|---|---|---|
| AISI 52100 | Bearing-grade; ferromagnetic | No nickel; not case-hardened (through-hardened); brittle core | Standard bearings (not gears/shafts) |
| JIS SUJ2 | Carbon-chromium alloy; wear-resistant | No nickel; through-hardened; lower toughness | Japanese automotive bearings |
| GCr15 | Bearing-grade; carbon-chromium | No nickel; through-hardened; poor impact resistance | Chinese industrial bearings |
| 100Cr6 | European standard; through-hardened | No nickel; brittle core; not for case hardening | Light-duty bearings |
| EN 100CrMo7 | Chromium-molybdenum alloy; wear-resistant | Low nickel; through-hardened; lower core toughness | Heavy-duty bearings (not gears) |
| AISI M50 | High-temperature strength | No nickel; through-hardened; for high-speed bearings | Aerospace turbine bearings |
| Stainless Steel (AISI 416) | Corrosion-resistant | Lower surface hardness; more expensive; weaker core | Food processing gears (wet environments) |
| Ceramic Components (Al₂O₃) | Wear-resistant | Brittle (no impact resistance); very expensive | High-precision, low-impact parts (not gears) |
| Plastic Components (PA66) | Corrosion-resistant | Low strength; no high-load use | Light-duty, low-speed parts (e.g., toy gears) |
Yigu Technology’s Perspective on EN 18NiCrMo14-6
At Yigu Technology, EN 18NiCrMo14-6 is our top choice for clients needing case-hardened parts like gears and shafts. Its nickel-molybdenum blend delivers the perfect balance of surface wear resistance and core toughness—critical for heavy automotive and mining applications. We use precise carburizing (controlling depth to ±0.1 mm) and post-heat treatment grinding to ensure parts meet tight tolerances. For clients in harsh environments, we add nitriding or zinc plating, making EN 18NiCrMo14-6 parts last 2–3x longer than standard case hardening steels.
FAQ About EN 18NiCrMo14-6 Case Hardening Steel
- What is the ideal case hardening depth for EN 18NiCrMo14-6?
It depends on the application: 0.8 – 1.2 mm for gears (balanced wear and flexibility), 1.5 – 2.0 mm for shafts/axles (higher wear resistance), and can be adjusted via carburizing time and temperature. - Can EN 18NiCrMo14-6 be used in corrosive environments?
It has moderate corrosion resistance. For wet or chemical-rich environments (e.g., marine or food processing), apply zinc plating or powder coating to prevent rust and extend service life. - How does EN 18NiCrMo14-6 differ from through-hardened steels like AISI 52100?
EN 18NiCrMo14-6 is case-hardened (hard surface, tough core) for wear + impact resistance, making it ideal for gears/shafts. AISI 52100 is through-hardened (uniformly hard, brittle core), better suited for bearings that don’t face heavy impact.
