Stainless Steel 1.4125
EN 1.4125
1.4125 (X105CrMo17, 440C, 9Cr18Mo) is a high-carbon 17% Cr martensitic stainless that hardens to very high hardness for wear-critical cutting and bearing parts.
Reference datasheet — 1.4125 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the +A condition
1.4125 tempers and conditions
1.4125 is supplied in 8 conditions, soft to hard. +A is the default FabDigit quotes; the values on this page are for it.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
+ADefault Annealed | Standard stock condition for machining before hardening; softest and most workable state. | 450 | 760 | 14 | 250 HB | — |
Annealed and cold drawn bar | Cold-drawn annealed bar for tight tolerance and better surface before hardening; slightly higher strength, lower ductility. | 650 | 880 | 10 | 29 HRC | — |
Hardened, tempered 450–550 °C | Used only when elevated-temperature stability is needed; corrosion resistance and toughness drop markedly. | 1,650 | 1,800 | 3 | 54 HRC | 2.7 % IACS |
Hardened, tempered 250–350 °C | Slightly lower hardness with better stress relief for larger tooling and valve components. | 1,790 | 1,900 | 3 | 56 HRC | — |
Quenched and tempered | Generic delivered hardened condition per EN 10088-3 for wear parts; specify tempering temperature for the exact hardness. | 1,900 | 1,970 | 2 | 58 HRC | — |
As-quenched | Intermediate state only — extremely brittle and stressed; always temper before service. | 1,900 | 2,000 | 0.5 | 63 HRC | — |
Hardened, tempered 150–200 °C | Maximum hardness with best corrosion resistance — standard for bearing races/balls and premium knife blades. | 1,930 | 2,030 | 2 | 59 HRC | — |
Hardened, deep-frozen (−80 °C) and tempered | Sub-zero treatment converts retained austenite for maximum hardness and dimensional stability in bearings and gauges. | 2,100 | 1 | 61 HRC | — |
What is 1.4125?
1.4125 (X105CrMo17, 440C, 9Cr18Mo) is a high-carbon 17% Cr martensitic stainless that hardens to very high hardness for wear-critical cutting and bearing parts. It is available annealed (+A, +A+C), in +QT and QT150/QT300/QT500 tempers, cryogenically treated and as-quenched, with 450 MPa yield, 760 MPa tensile, 14% elongation and 250 HB (99 HRB) in the default condition and a maximum service temperature of 650 °C. Weldability is essentially nil, formability is poor (score 25) and corrosion resistance is limited (score 35) — well below austenitic grades. For better corrosion behaviour in bearings, use 1.4123 (X40CrMoVN16-2). 1.4125 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 83% of stainless steel grades. It melts at 1,370°C (2,498 °F). 1.4125 has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 70% of stainless steel grades. Elongation at break is 14% and the elastic modulus is 200 GPa (29 Msi).
What is 1.4125 used for?
- knife blades
- surgical scalpels
- ball bearings
- wear-resistant valve parts
- precision gauges
Advantages
- High electrical conductivity — 2.9 % IACS, better than 87% of stainless steel grades
- Conducts heat well — 24 W/m·K (13.9 BTU/hr·ft·°F), better than 81% of stainless steel grades
Limitations
- Difficult to weld — 15/100, worse than 98% of stainless steel grades
- Needs corrosion protection — 35/100, worse than 97% of stainless steel grades
- Limited ductility — 14%, worse than 91% of stainless steel grades
- Hard to polish — 60/100, worse than 80% of stainless steel grades
- Limited formability — 25/100, worse than 78% of stainless steel grades
1.4125 properties
Typical room-temperature values for 1.4125-+A; bars are the position among stainless steel grades.
Physical3
1.4125 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 83% of stainless steel grades. It melts at 1,370°C (2,498 °F).
Mechanical14
1.4125 has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 70% of stainless steel grades. Elongation at break is 14% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
1.4125 is rated for continuous service to 650°C (1,202 °F). It conducts heat at 24 W/m·K (13.9 BTU/hr·ft·°F), better than 81% of stainless steel grades. Thermal expansion is 10.2 µm/m·K (5.67 µin/in·°F).
Electrical3
1.4125 conducts electricity at 2.9 % IACS, better than 87% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (35/100), worse than 97% of stainless steel grades.
Sustainability4
Producing a kilogram of 1.4125 takes about 55 MJ of energy and emits 5.2 kg of CO₂ — more than 50% of stainless steel grades. Typical recycled content is 60%.
Manufacturability7
1.4125's machinability is fair (35/100, better than 51% of stainless steel grades); weldability poor (15/100); formability poor (25/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. 1.4125 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 1.4125
Is 1.4125 easy to machine?
Machine only in the annealed condition with sharp carbide tooling, low speed and rigid setups; hardened parts require grinding or EDM.
Can 1.4125 be welded?
Essentially not recommended — high carbon causes cracking; if unavoidable preheat 250–350 °C, use matching or austenitic filler and immediately anneal/temper.
Can 1.4125 be formed, bent or molded?
Cold forming is very limited (annealed sheet only, generous radii); hot work 1100→850 °C followed by slow cool and spheroidize anneal.
1.4125 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| CEN 10088-3 X105CrMo17; GB 9Cr18Mo 0.95–1.10 | 0.95 – 1.2 | 1.05 |
| Si | ≤ 1 | 0.4 |
| Mn | ≤ 1 | 0.5 |
| P | ≤ 0.04 | |
| SEN often ≤0.015 for bearing/knife quality | ≤ 0.03 | |
| Cr | 16 – 18 | 17 |
| MoAISI 440C: Mo ≤ 0.75 | 0.4 – 0.8 | 0.55 |
| Niresidual | ≤ 0.5 | |
| Fe | balance |
What surface finishes work on 1.4125?
Takes a high mirror polish when fully hardened; passivate in nitric or citric acid after grinding, and avoid tempering above ~400 °C which degrades corrosion resistance.
Surface treatments FabDigit runs on stainless steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Passivation
Organic Coating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel 1.4125 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- EN / DIN / Werkstoff-Nr.
- X105CrMo17
- Similar grades
- 440C9Cr18Mo
How much does 1.4125 cost?
1.4125 is a premium-cost stainless steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
1.4125 — frequently asked
What is 1.4125 used for?
1.4125 is typically used for knife blades, surgical scalpels, ball bearings, wear-resistant valve parts and precision gauges. In short: hardest common stainless; 440C wear-resistance benchmark; not weldable, wear-first grade.
What is the yield strength of 1.4125?
1.4125 has a typical yield strength of 450 MPa (65.3 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 70% of stainless steel grades. Strength varies by condition: see the 8 listed tempers.
Is 1.4125 easy to machine?
Not especially — machinability is rated fair (35/100, better than 51% of stainless steel grades). Machine only in the annealed condition with sharp carbide tooling, low speed and rigid setups; hardened parts require grinding or EDM.
Can 1.4125 be welded?
Not readily — weldability is rated poor (15/100). Essentially not recommended — high carbon causes cracking; if unavoidable preheat 250–350 °C, use matching or austenitic filler and immediately anneal/temper.
What surface finishes work on 1.4125?
Takes a high mirror polish when fully hardened; passivate in nitric or citric acid after grinding, and avoid tempering above ~400 °C which degrades corrosion resistance.
Can 1.4125 be formed, bent or molded?
Cold forming is very limited (annealed sheet only, generous radii); hot work 1100→850 °C followed by slow cool and spheroidize anneal.
What is the maximum service temperature of 1.4125?
1.4125 is rated for continuous use to about 650°C (1,202 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 1.4125 +A and 1.4125-QT150?
+A is the default condition — standard stock condition for machining before hardening; softest and most workable state. QT150: maximum hardness with best corrosion resistance — standard for bearing races/balls and premium knife blades. Yield strength is 450 MPa in +A versus 1,930 MPa in QT150.
How much does 1.4125 cost?
1.4125 is a premium-cost stainless steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- EN 10088-3 Stainless steels – semi-finished products, bars, rods (X105CrMo17 / 1.4125) — CEN (2014)
- ASTM A276 / A484 Stainless Steel Bars and Shapes (Type 440C) — ASTM (2017)
- GB/T 1220 (9Cr18Mo) — SAC (2007)
- ASM Handbook Vol.1 Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Martensitic stainless bar/strip datasheets (Sandvik, Böhler N685, Aubert & Duval) — various producers (2023)
- 9Cr18Mo/440C — 1688 / Mysteel (2026)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.