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17NiCrMo6-4 steel is a high-performance case hardening steel classified in accordance with the European Union’s EN 10084 standard. This grade, with the German material number 1.6566, provides high surface wear resistance and hardness (after carburizing) thanks to its low-carbon structure, while maintaining high core toughness and strength.
This steel offers exceptional hardenability and core strength due to the balanced combination of critical alloying elements such as nickel (Ni), chromium (Cr), and molybdenum (Mo). It is especially ideal for machine parts that have complex geometries, are exposed to heavy loads, and require high wear resistance.
The combination of Ni, Cr, and Mo enables deep hardenability even in large cross-sections, allowing 17NiCrMo6-4 to deliver superior performance in highly loaded and critical components.
The chemical composition of 17NiCrMo6-4 steel strictly adheres to the international limits defined in the EN 10084 standard. These elements directly influence the steel’s hardenability, core strength, and toughness.
Carbon (C): 0.14–0.20%
• The most critical element determining surface hardness after case hardening.
• As carbon content increases, surface hardness and wear resistance improve.
• Carbon is kept low in the core to maintain toughness.
Silicon (Si): ≤ 0.40%
• Acts as a deoxidizer during melting (oxygen remover).
• Slightly increases strength, but its primary role is ensuring chemical cleanliness and a sound internal structure.
Manganese (Mn): 0.60–0.90%
• Increases tensile strength.
• Influences case-hardening depth, which is important in case hardening steels.
• Also supports hardenability.
Chromium (Cr): 0.80–1.10%
• Significantly increases hardenability.
• Contributes to wear resistance.
• Ensures more controlled hardening of both the surface and the core during heat treatment.
Nickel (Ni): 1.20–1.50%
• One of the most important alloying elements in this grade.
• Enhances core toughness and provides resistance to impact loads.
• The tough core + hard surface balance after case hardening is achieved largely thanks to nickel.
Molybdenum (Mo): 0.15–0.25%
• Prevents grain growth, ensuring homogeneous and controlled hardening.
• Increases high-temperature strength.
• Plays a critical role in maintaining hardenability stability in case hardening steels.
The most distinctive feature of this steel grade is the excellent balance between high surface hardness and core toughness achieved after heat treatment (carburizing, hardening, and tempering).
• Tensile Strength (Rm) – Minimum 1200 N/mm² for diameters ≤ 16 mm
Smaller diameters exhibit higher core strength due to faster cooling rates.
For diameters ≤ 16 mm, the steel provides a minimum tensile strength of 1200 N/mm², offering high resistance to fracture under heavy loads.
• Tensile Strength (Rm) – Minimum 1000 N/mm² for diameters 16–40 mm
As the diameter increases, the core cooling rate slows, resulting in slightly lower strength.
Even in the 16–40 mm range, the material still delivers at least 1000 N/mm² tensile strength, maintaining its high mechanical performance after heat treatment.
• Soft Annealed Hardness (+A Condition) – Maximum 229 HB
In the soft annealed (A) condition, the hardness is kept below 229 HB, ensuring improved machinability and ease of shaping during rough machining and forming operations.
• Typical Surface Hardness After Carburizing: 58–62 HRC
Carburizing results in a very high surface hardness of 58–62 HRC, providing excellent wear resistance.
The tough core maintains impact resistance, making the material ideal for gears, shafts, and components requiring high fatigue strength.
17NiCrMo6-4 is widely used in applications requiring high performance and exposure to heavy loads or abrasive conditions.
Hasçelik-produced 17NiCrMo6-4 (1.6566) steel is ideal for components demanding high surface hardness combined with core toughness.
• Automotive and Heavy Industry
Its alloy composition delivers exceptional durability for gearboxes, shafts, pins, and transmission components subjected to heavy loads.
• Mechanical Engineering
Used for pinions, camshafts, bushings, and various hydraulic/pneumatic components that operate under high contact pressure and friction.
• Agricultural and Earthmoving Machinery
Offers long service life and reliability in components where wear resistance is critical.
This steel grade is recognized under different standards across global markets. Knowing these equivalents is essential for procurement and technical documentation.
• USA (AISI/SAE): AISI 4317
• United Kingdom (BS): 817M17
• France (AFNOR): 18NCD6
• Italy (UNI, older): 18NiCrMo5
Common stock shapes for this alloyed case-hardening steel include:
• Round Bars: Used for shafts, pins, and small to medium-sized gears.
• Forged Blocks/Blanks: Preferred for large, critical, and heavily loaded components.
• Flat and Square Bars: Used in various machine parts and special tooling applications.
Hasçelik manufactures 17NiCrMo6-4 (1.6566) using customer-specific chemistry control, vacuum-sealed casting technology, and hot rolling with crack-control processes, ensuring suitability for demanding applications.
With Hasçelik’s HasPrime product line, this grade is supplied to industries seeking high internal cleanliness, superior surface homogeneity, and stable hardenability.
Customer-Specific Chemical Composition Management
Hasçelik steelworks can adjust the chemical composition of 17NiCrMo6-4 beyond standard limits to match application-specific needs such as carburizing depth, toughness, tensile strength, hardenability, and alloy optimization.
This enables customers to achieve maximum process efficiency with reduced scrap rates.
Vacuum-Sealed Casting Technology
Casting under vacuum conditions ensures:
• Low inclusion content
• Cleaner internal structure
• Excellent homogeneity
• Consistent heat-treatment response
This technology provides a significant quality advantage for case-hardening steels requiring superior internal and surface cleanliness.
Hot Rolling and Crack-Controlled Production
17NiCrMo6-4 produced in Hasçelik hot rolling lines undergoes multiple quality checks, including:
• Ultrasonic inspection
• Surface crack detection
• Dimensional accuracy monitoring
• Post-rolling straightness testing
Hasçelik Logistics Advantage – Global Supply Capability
With extensive warehousing in Türkiye and strong export infrastructure from Europe to the Middle East, the Americas, and Asia, Hasçelik delivers 17NiCrMo6-4 (1.6566) worldwide quickly and reliably.
Continuous stock management, on-time delivery, and flexible loading options ensure uninterrupted supply for our customers.
Why Choose Hasçelik 17NiCrMo6-4 Steel?
• Superior internal cleanliness with vacuum-sealed casting
• Customer-specific chemistry flexibility
• HasPrime crack-controlled production assurance
• Strong logistics network and global supply capability
• Engineering support for process–quality alignment
