EN 1.4125—also known as AISI 440C (AFNOR Z100CD17 / JIS SUS440C / X105CrMo17)—is a high-carbon, high-chromium martensitic stainless steel designed to deliver stainless properties combined with maximum hardness. After heat treatment, 1.4125 can reach the highest hardness level of the common stainless steel grades, resulting in excellent wear resistance and very good performance in rolling or sliding contact.
This makes 1.4125 a proven choice for bearing components (balls and races), precision wear parts and cutting applications where long service life is required. Corrosion resistance is good for a hardened stainless steel, but it remains below that of austenitic grades such as 1.4301 or 1.4404, especially in chloride-rich or marine environments. Final properties depend strongly on the delivered condition and the heat treatment route, and are confirmed on the EN 10204 / 3.1 inspection certificate.
| Element | Typical range (wt. %) |
|---|---|
| C | 0.95 – 1.20 |
| Cr | 16.0 – 18.0 |
| Mo | 0.40 – 0.80 |
| Si | ≤ 1.00 |
| Mn | ≤ 1.00 |
| P | ≤ 0.04 |
| S | ≤ 0.03 |
| Fe | Balance |
Exact chemical analysis is stated on the material certificate EN 10204 / 3.1.
| Property | Typical value (hardened & tempered) |
|---|---|
| Tensile strength (Rm) | per standard / see EN 10204 3.1 certificate (condition-dependent) |
| Yield strength (Rp0.2) | per standard / see EN 10204 3.1 certificate |
| Elongation (A5) | per standard / see EN 10204 3.1 certificate |
| Hardness | up to approx. 58 – 60 HRC (depending on heat treatment) |
| Wear resistance | very high (relative to stainless steels) |
Exact values are stated on the material certificate EN 10204 / 3.1.
1.4125 / 440C is supplied in multiple product forms, including bright drawn and ground round bar, hot rolled/forged and peeled/turned round bar, as well as forgings and sawn blocks/flat material from forged prime stock. Material is typically delivered in annealed condition for machining and then hardened and tempered to final properties. For precision components, ground tolerances and fixed lengths can be supplied depending on the product form.
Bright drawn / ground round bar: tolerance h9 according to DIN EN 10278, length 3 m
Stock sizes (bright bars): Ø 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 15.88, 16, 17, 18, 19.05, 20, 22.23, 25, 25.40, 28.50, 30, 31.75, 34.93, 35, 38, 39, 40, 41.28, 45.50, 49, 50.80, 54, 60, 63.50, 69.85, 73.03, 76.20 mm
Hot rolled / forged, peeled / turned round bar: according to DIN EN 10060, length 4 – 6 m
Stock sizes (peeled/turned): Ø 6.35, 7.94, 9.52, 10.16, 12.70, 14.30, 15.88, 19.05, 20, 22.23, 26.10, 28.58, 30, 32, 33, 35.35, 38.10, 40.23, 41.28, 44.70, 46.00, 46.53, 48.00, 50.80, 57.15, 58.69, 59.13, 60.52, 66.24, 70.18, 76.20, 80, 81, 82.55, 88.90, 95.25, 101.60, 106, 110, 114.30, 120.65, 126, 127, 130, 133.35, 139.70, 146.05, 160, 165.10, 180, 203.20, 230, 241.29, 260, 280, 310 mm
Notes: Bright bars are supplied only in full lengths (not cut). Peeled material can also be supplied in fixed lengths on request.
Centerless grinding available on request. This is commonly specified for bearing shafts and wear parts where tight diameter tolerances and a high-quality surface finish are required. Provide target diameter, tolerance, straightness and surface roughness requirements at quotation stage.
Thanks to its very high achievable hardness and wear resistance, 1.4125 / 440C is widely used for:
For corrosion-critical environments, especially with chlorides or seawater exposure, consider higher corrosion-resistant stainless or nickel alloys depending on the service conditions.
440C contains a high level of carbon and chromium. After hardening and tempering, it forms a hard martensitic matrix with chromium-rich carbides, which significantly improves abrasion resistance and rolling contact fatigue performance. This is why it is widely used for bearing parts and wear components.
Depending on the heat treatment route and section size, 1.4125 can reach approximately 58–60 HRC. The achieved hardness and mechanical test results depend on the condition and are stated on the EN 10204 / 3.1 certificate when applicable.
440C offers good corrosion resistance compared to other hardened stainless steels, but it is generally not comparable to austenitic grades such as 1.4301 (304) or 1.4404 (316L), especially in chloride-rich environments. Corrosion resistance is strongly influenced by surface finish, cleanliness, passivation and the heat treatment condition.
Machining is normally performed in the annealed condition. After hardening, the material becomes very hard and machining becomes difficult; final sizing is typically done by grinding. This is one reason why precision parts are often supplied as ground bar or centerless ground shafts.
Yes. Common supply includes bright drawn / ground round bar (often in tolerance h9 according to DIN EN 10278, length 3 m) and hot rolled/forged peeled or turned round bar according to DIN EN 10060 (typically length 4–6 m). Availability depends on size and stock situation.
Yes. Forgings such as bars, discs and rings can be supplied to drawing on request. Blocks/flat material sawn from forged prime material are also available on request. Provide drawings, required condition and inspection requirements when requesting a quotation.
Yes. Material is supplied with EN 10204 / 3.1 certification. The certificate confirms chemical analysis, delivered condition and relevant mechanical test results for traceability and quality assurance.
Certificates: EN 10204 / 3.1
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