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| Grade | Code | AISI | Martensitic Stainless Steel |
| 1.4125 | X105CrMo17 | 440C |
1.4125/440C is a martensitic stainless steel grade that can be hardened by heat treatment. It is distinguished by high hardness, wear resistance, mechanical strength and the ability to retain a sharp edge. The grade performs best in the hardened and tempered condition and is magnetic; due to its high hardness, machining and welding require carefully controlled process conditions.
| C % | Si % | Mn % | P % | S % | Cr % | Mo % |
| 0.95–1.20 | ≤1.00 | ≤1.00 | ≤0.040 | ≤0.030 | 16.00–18.00 | 0.40–0.80 |
| Product form | Rp0.2 [MPa] | Rm [MPa] | Elongation [%] | Hardness [HB] | Density [g/cm³] |
| Bar | ≈448 | ≈758 | ≈14 | ≤285 | 7.70 |
| Plate | ≈448 | ≈758 | ≈14 | ≤285 | 7.70 |
| Sector | Most common products |
| Bearing and motion systems | Bearing balls, inner and outer bearing rings, roller bearing elements |
| Pump and valve systems | Valve seats, valve balls, pump wear components |
| Knives and cutting tools | Industrial knives, razor and cutting edges, chisels |
| Medical and dental | Surgical cutting blades, surgical scissors, dental cutting instruments |
| Food processing | Food-cutting blades, meat-slicing blades, packaging-machine cutting edges |
| Mould and plastics | Injection-mould nozzles, dies and punches, mould inserts |
| Precision measurement and instrumentation | Gauges, measuring instrument components, precision fixtures |
| Textile machinery | Thread guides, textile cutting blades, wear-resistant bushings |
| Aerospace and defence | Precision radial bearings, sealed bearings, pallet and guide rollers |
| General machinery manufacturing | Wear bushings, bearing sleeves, precision shafts |
1.4125 grade performance is governed not only by the material's chemical composition, but also by the heat treatment applied and the final surface quality. The martensitic structure produced during hardening, together with the chromium-molybdenum carbides within the microstructure, provides high wear resistance and hardness that remains stable over extended periods. Incorrect temperature, holding time or cooling practice, however, can lead to retained austenite, coarse carbide formation, dimensional change and cracking. Parts should therefore be rough-machined first in the annealed condition, then hardened and tempered at low temperature, and finally brought to their finished dimensions by grinding or precision finishing. To preserve corrosion performance, grinding burns should be avoided; the surface should be properly polished and passivated when required. At the purchasing stage, specifying only the grade designation "1.4125" is not sufficient; the delivery condition, target hardness, heat-treatment condition and surface quality should also be stated clearly.
1.4125, AISI 440C, X105CrMo17
| Product form | ASTM | AMS | DIN/EN |
| Bar | ASTM A276/A276M – Type 440C / UNS S44004 | AMS 5630 – standard grade, AMS 5618 – vacuum-remelted grade, AMS 5880 – bearing grade | DIN EN 10088-3 – X105CrMo17 / 1.4125 |
| Plate | ASTM A240/A240M – Type 440C / UNS S44004 | No dedicated AMS standard directly covering plate products is available | DIN EN 10088-2 – X105CrMo17 / 1.4125 |
17-7PH – It is the closest option because it can be hardened by heat treatment and offers high hardness potential.
13-8PH – It may be considered for parts requiring a combination of high strength, toughness and dimensional stability.
15-5PH – It is a suitable alternative in terms of high strength, corrosion resistance and availability.
voestalpine BÖHLER Edelstahl – BÖHLER N695 / 1.4125 / AISI 440C
Gloria Material Technology Corp. – 440C / 1.4125 / X105CrMo17
Swiss Steel Group – 1.4125 / X105CrMo17 / AISI 440C
Note: The information contained in this datasheet is for informational purposes only; no liability is accepted.
