Steel 718 · finish state
Steel 718 Nitrided
Properties of the Nitrided condition, compared with the other 718 tempers.
Post-machining surface treatment for wear and gas-erosion resistance on slides, gates and glass-filled-resin cavities.
What is 718 Nitrided?
718 Nitrided is 718 supplied in the Nitrided condition — post-machining surface treatment for wear and gas-erosion resistance on slides, gates and glass-filled-resin cavities. 718 Nitrided has a yield strength of 880 MPa (128 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 90% of steel grades. Elongation at break is 14% and the elastic modulus is 205 GPa (29.7 Msi). 718 Nitrided has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F). Prehard is the default condition FabDigit quotes; Nitrided is available on request or by drawing note.
Advantages
- Good corrosion resistance — 25/100, better than 91% of steel grades
- High strength — 880 MPa (128 ksi), better than 90% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- High service temperature — 450°C (842 °F), better than 86% of steel grades
Limitations
- Difficult to machine — 10/100, worse than 100% of steel grades
- Difficult to weld — 10/100, worse than 99% of steel grades
- Limited formability — 15/100, worse than 87% of steel grades
- Poor heat conductor — 32 W/m·K (18.5 BTU/hr·ft·°F), worse than 82% of steel grades
- Limited ductility — 14%, worse than 75% of steel grades
718 Nitrided properties
Typical room-temperature values for 718 Nitrided — 8 properties are specific to this condition; the rest are grade-level values shared by every 718 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
718 Nitrided has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
718 Nitrided has a yield strength of 880 MPa (128 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 90% of steel grades. Elongation at break is 14% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
718 Nitrided is rated for continuous service to 450°C (842 °F). It conducts heat at 32 W/m·K (18.5 BTU/hr·ft·°F), worse than 82% of steel grades. Thermal expansion is 12.6 µm/m·K (7 µin/in·°F).
Electrical2
718 Nitrided has an electrical resistivity of 2.2×10⁻⁷ Ω·m.
Chemical & Environmental2
Corrosion resistance is poor (25/100), better than 91% of steel grades.
Sustainability4
Producing a kilogram of 718 Nitrided takes about 32 MJ of energy and emits 2.3 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 30%.
Manufacturability7
718 Nitrided's machinability is not recommended (10/100, worse than 100% of steel grades); weldability not recommended (10/100); formability poor (15/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 718 tempers and conditions
718 is also supplied in 5 other conditions. The full side-by-side table is on the 718 overview.
- PrehardDefaultStandard stock condition: machine the cavity directly, no heat treatment or size-change risk.880 MPa yield · 32 HRC
- Q&T-40Used only on small inserts/cores that are re-austenitized (~850 °C, oil) and low-tempered for extra strength; expect distortion and lower toughness.1,150 MPa yield · 41 HRC
- NitridedPost-machining surface treatment for wear and gas-erosion resistance on slides, gates and glass-filled-resin cavities.1,030 MPa tensile
- Prehard-HChoose when the mould runs abrasive filled resins or needs better cavity wear/dent resistance while still machinable prehard.1,000 MPa yield · 36 HRC
- Prehard-SPick for optical/high-gloss cavities and photo-etched textures where inclusion streaks and polish defects are unacceptable.880 MPa yield · 32 HRC
- AnnealedPick when you intend to rough-machine deep cavities and then quench-and-temper or carburize/nitride yourself.450 MPa yield · 215 HB
Working with 718 Nitrided
Is 718 easy to machine?
Machines predictably at 30–34 HRC with coated carbide (≈120–180 m/min milling, rigid setups); use positive geometry and adequate coolant to avoid work-hardened glaze in deep pockets.
Can 718 be welded?
Repair-weldable with matching or low-alloy Ni filler: preheat/interpass 250–325 °C, slow cool, then temper ~30 °C below the original tempering temperature to restore hardness match.
Can 718 be formed, bent or molded?
Supplied as prehard blocks/plate — not a cold-forming product; hot work at 850–1100 °C with slow cooling if reforging is required.
What surface finishes work on 718?
Excellent mirror-polish and photo-etch response; protect with hard chrome, EN Ni-P or nitriding for wear and rust resistance, and keep cooling channels inhibited.
718 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 |
|---|---|---|
| C | 0.35 – 0.45 | 0.4 |
| Si | 0.2 – 0.4 | 0.3 |
| Mn | 1.3 – 1.6 | 1.45 |
| Cr | 1.8 – 2.1 | 1.95 |
| Mo | 0.15 – 0.25 | 0.2 |
| NiNi addition over P20 for through-hardening of thick blocks | 0.9 – 1.2 | 1.05 |
| P | ≤ 0.03 | — |
| Smax; some grades add S ~0.05–0.10 for free-machining | ≤ 0.03 | — |
| Fe | balance | — |
718 Nitrided — frequently asked
What is 718 Nitrided used for?
718 Nitrided is typically used for large injection mould cavity and core plates, mould bases and bolster plates, mould inserts, blow mould bodies, die-casting die holders and textured cosmetic cavities for automotive interior parts. In short: workhorse mold-base plate.
What is the yield strength of 718 Nitrided?
718 Nitrided has a typical yield strength of 880 MPa (128 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 90% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is 718 Nitrided easy to machine?
Not especially — machinability is rated not recommended (10/100, worse than 100% of steel grades). Machines predictably at 30–34 HRC with coated carbide (≈120–180 m/min milling, rigid setups); use positive geometry and adequate coolant to avoid work-hardened glaze in deep pockets.
Can 718 Nitrided be welded?
Not readily — weldability is rated not recommended (10/100). Repair-weldable with matching or low-alloy Ni filler: preheat/interpass 250–325 °C, slow cool, then temper ~30 °C below the original tempering temperature to restore hardness match.
What surface finishes work on 718 Nitrided?
Excellent mirror-polish and photo-etch response; protect with hard chrome, EN Ni-P or nitriding for wear and rust resistance, and keep cooling channels inhibited.
Can 718 Nitrided be formed, bent or molded?
Supplied as prehard blocks/plate — not a cold-forming product; hot work at 850–1100 °C with slow cooling if reforging is required.
What is the maximum service temperature of 718 Nitrided?
718 Nitrided is rated for continuous use to about 450°C (842 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in 718 Nitrided?
Yes — 718 Nitrided is available for CNC machining with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- DIN EN ISO 4957 — Tool steels (40CrMnNiMo8-6-4 / 1.2738) — ISO/DIN (2018)
- Uddeholm Impax Supreme (P20+Ni prehardened mould steel) — Uddeholm/ASSAB (2020)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Specialty Handbook: Tool Materials — ASM International (1995)
- GB/T 1299 — Tool and die steels (3Cr2MnNiMo) — SAC (2014)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.