AISI 440C
AISI 440C Stainless Steel: A Martensitic Alloy Designed Specifically for High Hardness and Wear Resistance
AISI 440C is a stainless steel grade with a high carbon content, a martensitic structure, resistance to corrosion and extremely high durability against wear. Unlike most conventional stainless steels, this alloy stands out particularly in applications requiring hardness, wear resistance and surface quality. At the same time, with its hardness that can exceed 60 HRC when heat treated, it is preferred in engineering fields demanding high performance.
In this article the chemical and mechanical properties of AISI 440C, its compliance with international norms, its application areas, its advantages and its disadvantages will be addressed at a technical level; terms that may be important for purchasing decisions will be included naturally.
AISI 440C Chemical Composition and Microstructural Properties
AISI 440C is one of the members of the martensitic stainless steel class with the highest carbon content. This high carbon ratio gives the steel extraordinary hardness, especially after heat treatment.
Its typical chemical composition:
- Carbon (C): 0.95% – 1.20%
- Chromium (Cr): 16.0% – 18.0%
- Manganese (Mn): Max. 1.0%
- Silicon (Si): Max. 1.0%
- Molybdenum (Mo): Max. 0.75%
- Phosphorus (P): Max. 0.04%
- Sulphur (S): Max. 0.03%
While the high carbon amount offers a great advantage especially in applications that call for a hard surface, the chromium content provides a medium level of corrosion resistance. The essential success of this alloy, however, is that it shows superior performance in abrasive environments while preserving its surface hardness.
AISI 440C Heat Treatment and Mechanical Properties
AISI 440C is one of the rare stainless steel grades that can be hardened with suitable heat treatment up to a level of maximum 60-62 HRC. For this reason expressions such as “AISI 440C heat treated” or “440C hardened stainless round bar” play an important role in defining technical requirements during the purchasing process.
Typical heat treatment parameters:
- Austenitising temperature: 1010 – 1065 °C
- Cooling medium: Air or oil
- Tempering temperature: 150 – 250 °C
Mechanical properties after heat treatment:
- Tensile strength (UTS): 760 – 1950 MPa
- Yield strength (0.2% offset): 450 – 1700 MPa
- Hardness: 58 – 62 HRC
- Elongation: 2% – 5% (low because of the brittle structure)
- Wear resistance: Very high
These properties make AISI 440C ideal for applications such as mould parts, ball bearings, blades and valve components that demand high precision and surface strength.
ASTM, AMS and Other International Standards
AISI 440C stainless steel has been defined in various industry standards. Compliance with these norms is of vital importance for material supply and quality control.
ASTM Standards:
- ASTM A276 – Bar and section products
- ASTM A479 – Bar products for pressure vessels
- ASTM A314 – General purpose stainless bars
- ASTM A582 – Pressed bar products for tool parts
AMS Standards:
- AMS 5630 – AISI 440C bar products in the annealed condition
- AMS 5880 – Hardened 440C steels for use in aircraft structures
DIN / EN Equivalent:
- DIN 1.4125 / X105CrMo17
- EN 10088-1 compliant with the standard
These standards are important for quality assurance, especially in sectors such as aerospace, the defence industry, precision engineering and automotive. Technical expressions such as “AMS 5630 440C bar” or “ASTM A276 440C shaft” frequently appear in project and purchasing documents.
Areas of Use of AISI 440C
The high surface hardness and wear resistance of AISI 440C make it indispensable particularly in the following sectors:
- Bearing and Journal Systems: It is preferred in ball bearings, roller bearings and precision rotating elements, in systems that both operate under mechanical load and demand low friction.
- Cutting Tools and Industrial Blades: Industrial blades cutting metal, plastic and paper benefit from the high hardness and edge retention capability of 440C.
- Mould and Forming Parts: Companies seeking material with high surface strength for injection moulds, press moulds and forming equipment generally search for “440C mould steel price”.
- Aerospace and Defence Industry: AMS certified 440C products are preferred for parts with precise tolerances that carry high loads (shafts, pins, valves).
- Food Processing and Medical Instruments: Thanks to its reasonable resistance to rusting and its excellent edge sharpness, it is used in blades and sterilisable surgical equipment.
Advantages and Disadvantages
Advantages:
- Extraordinary wear resistance with hardness above 60 HRC
- Excellent surface strength through heat treatment
- Medium level corrosion resistance
- An aesthetic surface can be obtained thanks to its polishability
- It can be machined with very low deformation
Disadvantages:
- Because of its brittle structure it is not suitable for impact loads
- Its weldability is low
- Its ductility is quite limited (especially in the hardened condition)
- Risk of pitting corrosion in chlorinated environments
- It may cause tool wear in deep cutting operations
Purchasing and Logistics Criteria
In the commercial market AISI 440C is generally supplied in the annealed, hardened or semi-machined condition as round bar, flat bar or plate. In import processes it is generally assessed under HS Code 7222.20 and a TSE certificate or an EN 10204 3.1 certificate may be requested.
Conclusion
AISI 440C is one of the hardest and most wear resistant material grades within the martensitic stainless steel family. However, this hardness and strength make it suitable only for certain applications. In parts requiring high surface strength, such as precision bearings, cutting tools and moulds, it offers long-life and reliable solutions with the correct heat treatment and careful machining.
In project and purchasing processes, seeking compliance with the ASTM A276, AMS 5630 or DIN 1.4125 standards provides a safe investment in terms of quality and performance.
#ASTMA276
#ASTMA479
#ASTMA314
#ASTMA582
#AMS5630
#AMS5880
#DIN1.4125
#X105CrMo17
#EN10088
We supply this material
We supply AISI 440C (1.4125) — to AMS 5630, AMS 5618 standards, in the dimensions and forms required. Contact us for stock availability and pricing.
Similar products
4340 VAR · AISI 410 · AISI 415 · AISI 416 · Martensitic steels →