Stainless Steel 418-H (Hardened)
Heat-treated state
AISI/SAE 418 · UNS S41800
Interim condition only — must be tempered promptly; brittle and prone to quench cracking.
Values for the H condition
Other 418 tempers and conditions
418 is listed in 6 conditions; see the grade overview at 418.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest supply condition for rough machining and hot-worked stock before final hardening. | 620 | 830 | 22 | 22 HRC | — |
Cold drawn, annealed | Cold-finished annealed bar for close tolerance blanks that will be hardened afterwards. | 720 | 900 | 16 | 27 HRC | 2.5 % IACS |
Q&T-650Default Hardened and tempered ~650 °C | Default aerospace/turbine condition: best balance of ~1070 MPa strength, ductility and thermal stability to 590 °C. | 860 | 1,070 | 18 | 34 HRC | — |
Hardened and tempered ~620 °C | Intermediate temper for higher blade-root and fastener strength with still-adequate toughness. | 1,000 | 1,210 | 16 | 38 HRC | — |
Hardened and tempered ~540 °C | Choose for maximum strength/wear in short-life or lightly loaded-in-impact parts; toughness and corrosion resistance drop. | 1,140 | 1,380 | 13 | 42 HRC | — |
HThis page Hardened | Interim condition only — must be tempered promptly; brittle and prone to quench cracking. | 1,200 | 1,550 | 8 | 46 HRC | 2.3 % IACS |
What is 418-H?
418-H is 418 heat treated to H — interim condition only — must be tempered promptly; brittle and prone to quench cracking. 418-H has a yield strength of 1,200 MPa (174 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 98% of stainless steel grades. Elongation at break is 8% and the elastic modulus is 215 GPa (31.2 Msi). 418-H has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,425°C (2,597 °F). Q&T-650 is the default condition FabDigit quotes; H is available on request or by drawing note.
Advantages
- High strength — 1,200 MPa (174 ksi), better than 98% of stainless steel grades
- Conducts heat well — 22 W/m·K (12.7 BTU/hr·ft·°F), better than 77% of stainless steel grades
Limitations
- Difficult to machine — 12/100, worse than 100% of stainless steel grades
- Difficult to weld — 10/100, worse than 100% of stainless steel grades
- Limited ductility — 8%, worse than 99% of stainless steel grades
- Low fracture toughness — 25 MPa·√m (22.8 ksi·√in), worse than 99% of stainless steel grades
- Limited service temperature — 250°C (482 °F), worse than 99% of stainless steel grades
418-H properties
Typical room-temperature values for 418-H; 22 are specific to this condition. Other listed values are 418 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
418-H has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
418-H has a yield strength of 1,200 MPa (174 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 98% of stainless steel grades. Elongation at break is 8% and the elastic modulus is 215 GPa (31.2 Msi).
Thermal6
418-H is rated for continuous service to 250°C (482 °F). It conducts heat at 22 W/m·K (12.7 BTU/hr·ft·°F), better than 77% of stainless steel grades. Thermal expansion is 10.6 µm/m·K (5.89 µin/in·°F).
Electrical3
418-H conducts electricity at 2.3 % IACS, better than 55% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (50/100), worse than 78% of stainless steel grades.
Sustainability4
Producing a kilogram of 418-H takes about 57 MJ of energy and emits 5.2 kg of CO₂ — more than 62% of stainless steel grades. Typical recycled content is 35%.
Manufacturability8
418-H's machinability is not recommended (12/100, worse than 100% of stainless steel grades); weldability not recommended (10/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 418-H
Is 418 easy to machine?
Machine in the annealed or high-temper (32–38 HRC) condition with rigid setups, sharp carbide tooling, slow speeds and heavy positive feeds; work hardens and is abrasive due to the tungsten content.
Can 418 be welded?
Weldable by GTAW/GMAW with matching or 410/309 filler, but requires 200–300 °C preheat, controlled interpass and a full post-weld temper to avoid hard, cracking-prone martensitic HAZ.
Can 418 be formed, bent or molded?
Hot work at 1050–1150 °C and slow cool/anneal; cold forming is limited to mild bending of annealed stock only.
What surface finishes work on 418?
Passivate (ASTM A967 nitric or citric) after machining; takes a good polish and accepts hard chrome, nitriding or high-temperature aluminide coatings for erosion protection.
418 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 | 0.15 – 0.2 | 0.17 |
| Mn | ≤ 0.5 | 0.35 |
| Si | ≤ 0.5 | 0.3 |
| Pimpurity limit | ≤ 0.04 | — |
| Simpurity limit | ≤ 0.03 | — |
| Cr | 12 – 14 | 13 |
| Ni | 1.8 – 2.2 | 2 |
| Wtungsten gives elevated-temperature strength | 2.5 – 3.5 | 3 |
| Fe | balance | — |
418-H — frequently asked
What is 418-H used for?
418-H is typically used for steam turbine blades, gas turbine blading and vanes, high-temperature fasteners, turbine rotor blade roots, compressor blades and highly stressed shafts and pins. In short: strongest grade in family; tungsten-strengthened, hot-strong; turbine blading standard.
What is the yield strength of 418-H?
418-H has a typical yield strength of 1,200 MPa (174 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 98% of stainless steel grades. Strength varies by condition: see the 6 listed tempers.
Is 418-H easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 100% of stainless steel grades). Machine in the annealed or high-temper (32–38 HRC) condition with rigid setups, sharp carbide tooling, slow speeds and heavy positive feeds; work hardens and is abrasive due to the tungsten content.
Can 418-H be welded?
Not readily — weldability is rated not recommended (10/100). Weldable by GTAW/GMAW with matching or 410/309 filler, but requires 200–300 °C preheat, controlled interpass and a full post-weld temper to avoid hard, cracking-prone martensitic HAZ.
What surface finishes work on 418-H?
Passivate (ASTM A967 nitric or citric) after machining; takes a good polish and accepts hard chrome, nitriding or high-temperature aluminide coatings for erosion protection.
Can 418-H be formed, bent or molded?
Hot work at 1050–1150 °C and slow cool/anneal; cold forming is limited to mild bending of annealed stock only.
What is the maximum service temperature of 418-H?
418-H is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 418 Q&T-650 and 418-H?
Q&T-650 is the default condition — default aerospace/turbine condition: best balance of ~1070 MPa strength, ductility and thermal stability to 590 °C. H: interim condition only — must be tempered promptly; brittle and prone to quench cracking. Yield strength is 860 MPa in Q&T-650 versus 1,200 MPa in H.
Sources
- AMS 5616 — Steel, Corrosion and Heat Resistant, Bars, Wire and Forgings 13Cr-2.0Ni-3.0W — SAE International (2018)
- ASTM A565/A565M — Martensitic Stainless Steel Bars for High-Temperature Service (Grade 615) — ASTM (2019)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Specialty Handbook — Stainless Steels — ASM International (1994)
- Greek Ascoloy (Type 418 / UNS S41800) alloy data sheet — specialty steel producer (2020)
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.