Stainless Steel Discaloy
UNS S66220
Discaloy (S66220) is an early iron-base, age-hardenable superalloy closely related to A-286, using an austenitic Fe-Ni-Cr matrix with titanium-based precipitation strengthening.
Reference datasheet — Discaloy 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 STA condition
Discaloy tempers and conditions
Discaloy is supplied in 5 conditions, soft to hard. STA is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition, used for forming, machining of complex shapes and welding before aging. | 300 | 700 | 40 | 190 HB | — |
Hot rolled | Mill product form supplied for re-forging or subsequent full heat treatment; properties not guaranteed. | 450 | 800 | 30 | 20 HRC | 1.9 % IACS |
ST + single age | Simplified single-step age; slightly lower strength but better ductility and notch toughness than double aging. | 660 | 940 | 23 | 28 HRC | 1.9 % IACS |
STADefault Solution treated and aged | Standard supply and service condition for turbine discs, bolts and shafts needing strength to ~650 °C. | 730 | 1,000 | 20 | 30 HRC | — |
Cold drawn | Choose for fasteners and springs where cold work plus subsequent aging gives the highest room-temperature strength. | 950 | 1,150 | 12 | 35 HRC | 1.9 % IACS |
What is Discaloy?
Discaloy (S66220) is an early iron-base, age-hardenable superalloy closely related to A-286, using an austenitic Fe-Ni-Cr matrix with titanium-based precipitation strengthening. It is used for hot-section rotating and bolted hardware where 650 °C strength and oxidation resistance are needed at lower cost than nickel-base alloys; forged discs, bar and bolting stock give about 730 MPa yield, 1000 MPa tensile, 20 % elongation and 290 HB (30 HRC). Machinability (18) and formability (25) are poor, welding is limited by strain-age cracking, and A-286 is the more widely stocked equivalent. Discaloy has a density of 7.97 g/cm³ (0.288 lb/in³), heavier than 83% of stainless steel grades. It melts at 1,380°C (2,516 °F). Discaloy has a yield strength of 730 MPa (106 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 93% of stainless steel grades. Elongation at break is 20% and the elastic modulus is 196 GPa (28.4 Msi).
What is Discaloy used for?
- gas turbine discs
- turbine bolting
- high-temperature fasteners
Advantages
- High strength — 730 MPa (106 ksi), better than 93% of stainless steel grades
Limitations
- Difficult to machine — 18/100, worse than 99% of stainless steel grades
- Difficult to weld — 35/100, worse than 86% of stainless steel grades
- Low electrical conductivity — 1.9 % IACS, worse than 84% of stainless steel grades
- Limited ductility — 20%, worse than 79% of stainless steel grades
- Limited formability — 25/100, worse than 78% of stainless steel grades
Discaloy properties
Typical room-temperature values for Discaloy-STA; bars are the position among stainless steel grades.
Physical3
Discaloy has a density of 7.97 g/cm³ (0.288 lb/in³), heavier than 83% of stainless steel grades. It melts at 1,380°C (2,516 °F).
Mechanical14
Discaloy has a yield strength of 730 MPa (106 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 93% of stainless steel grades. Elongation at break is 20% and the elastic modulus is 196 GPa (28.4 Msi).
Thermal5
Discaloy is rated for continuous service to 650°C (1,202 °F). It conducts heat at 14 W/m·K (8.09 BTU/hr·ft·°F), worse than 80% of stainless steel grades. Thermal expansion is 15.5 µm/m·K (8.61 µin/in·°F).
Electrical3
Discaloy conducts electricity at 1.9 % IACS, worse than 84% of stainless steel grades.
Chemical & Environmental2
Corrosion resistance is good (62/100), worse than 52% of stainless steel grades.
Sustainability4
Producing a kilogram of Discaloy takes about 80 MJ of energy and emits 5.5 kg of CO₂ — more than 89% of stainless steel grades. Typical recycled content is 35%.
Manufacturability8
Discaloy's machinability is poor (18/100, worse than 99% of stainless steel grades); weldability fair (35/100); 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. Discaloy is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Discaloy
Is Discaloy easy to machine?
Machine in the solution-treated state where possible: rigid setups, positive-rake carbide or ceramic tools, low speed/heavy feed, flood coolant — the alloy work-hardens rapidly and is abrasive when aged.
Can Discaloy be welded?
GTAW/EBW in the solution-treated condition with A-286-type or Ni-base filler, then full solution + age; avoid welding aged material because of strain-age (post-weld heat-treat) cracking.
Can Discaloy be formed, bent or molded?
Hot work at roughly 1050–1150 °C with finish above ~950 °C; cold forming only in the solution-treated condition with interstage anneals.
Discaloy 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 |
|---|---|---|
| Clow carbon to avoid excessive carbide | ≤ 0.08 | 0.04 |
| Mn | 0.35 – 1.5 | 0.9 |
| Si | ≤ 1 | 0.6 |
| P | ≤ 0.04 | |
| S | ≤ 0.03 | |
| Croxidation resistance | 13 – 15 | 13.8 |
| Niaustenite stabiliser, γ′ former | 24 – 27 | 26 |
| Mosolid-solution strengthening | 2.5 – 3.5 | 2.75 |
| Tiγ′ Ni₃(Al,Ti) former | 1.5 – 2 | 1.75 |
| Al | ≤ 0.35 | 0.15 |
| Bgrain-boundary strengthening | 0 – 0.01 | 0.01 |
| Febalance, ≈54 % | balance |
What surface finishes work on Discaloy?
Passivate or leave as ground/polished; for extended service above ~700 °C use aluminide or MCrAlY-type protective coatings. No anodizing.
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 Discaloy in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S66220
How much does Discaloy cost?
Discaloy is a high-cost stainless steel ($$$$), pricier than about 78% 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.
Discaloy — frequently asked
What is Discaloy used for?
Discaloy is typically used for gas turbine discs, turbine bolting and high-temperature fasteners. In short: A-286-class iron-base superalloy; 650 °C bolting strength; cheaper than nickel-base alloys.
What is the yield strength of Discaloy?
Discaloy has a typical yield strength of 730 MPa (106 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 93% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is Discaloy easy to machine?
Not especially — machinability is rated poor (18/100, worse than 99% of stainless steel grades). Machine in the solution-treated state where possible: rigid setups, positive-rake carbide or ceramic tools, low speed/heavy feed, flood coolant — the alloy work-hardens rapidly and is abrasive when aged.
Can Discaloy be welded?
With care — weldability is rated fair (35/100). GTAW/EBW in the solution-treated condition with A-286-type or Ni-base filler, then full solution + age; avoid welding aged material because of strain-age (post-weld heat-treat) cracking.
What surface finishes work on Discaloy?
Passivate or leave as ground/polished; for extended service above ~700 °C use aluminide or MCrAlY-type protective coatings. No anodizing.
Can Discaloy be formed, bent or molded?
Hot work at roughly 1050–1150 °C with finish above ~950 °C; cold forming only in the solution-treated condition with interstage anneals.
What is the maximum service temperature of Discaloy?
Discaloy 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 Discaloy-STA and Discaloy-SA?
STA is the default condition — standard supply and service condition for turbine discs, bolts and shafts needing strength to ~650 °C. SA: softest condition, used for forming, machining of complex shapes and welding before aging. Yield strength is 730 MPa in STA versus 300 MPa in SA.
How much does Discaloy cost?
Discaloy is a high-cost stainless steel ($$$$), pricier than about 78% 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
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys (heat-resistant Fe-Ni-Cr alloys) — ASM International (1990)
- Superalloys: A Technical Guide, 2nd ed. — ASM International (2002)
- SAE HS-1086 / Metals & Alloys in the Unified Numbering System (UNS S66220) — SAE International / ASTM (2017)
- Aerospace Structural Metals Handbook — iron-base heat-resistant alloys — CINDAS/Purdue (1998)
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.