Stainless Steel Alloy 864
UNS S35135
Alloy 864 (S35135) is a nickel-iron-chromium superaustenitic alloy engineered for high-temperature strength and resistance to carburizing and oxidizing atmospheres, used as an upgrade material in thermal processing equipment.
Reference datasheet — Alloy 864 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 Annealed condition
Alloy 864 tempers and conditions
Alloy 864 is supplied in 7 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Hot Rolled, Annealed and Pickled | Heavier sections for furnace fixtures, retorts and radiant tubes; slightly lower strength and coarser grain than cold-rolled annealed strip. | 270 | 600 | 45 | 165 HB | 1.7 % IACS |
AnnealedDefault Annealed (solution annealed, sheet/strip/tube) | Standard stocked condition: maximum ductility for bellows/flex-tube forming and best corrosion/oxidation performance. | 290 | 620 | 45 | 170 HB | — |
Cold drawn | Choose for close-tolerance bar and tube where higher yield strength and better surface finish are needed than annealed. | 520 | 760 | 25 | 20 HRC | 1.7 % IACS |
Stress relieved | Use when cold-formed bellows or springs need residual stress reduction and dimensional stability before hot service. | 600 | 830 | 20 | 23 HRC | 1.7 % IACS |
Cold Worked, 1/4 Hard | Light temper for spring-back-controlled clamps, gaskets and formed parts needing extra stiffness. | 620 | 830 | 18 | 25 HRC | 1.7 % IACS |
Cold Worked, 1/2 Hard | Higher-strength strip/wire for clamps, mesh and springs used below the recrystallization range. | 760 | 965 | 10 | 31 HRC | 1.7 % IACS |
Cold Worked, Full Hard / Spring temper | Maximum strength condition for wire, springs and braid used in exhaust flex couplings; very limited ductility. | 965 | 1,150 | 5 | 36 HRC | 1.7 % IACS |
Supply forms, finishes and certifications
Ways Alloy 864 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
BA | Bright Annealed | Surface finish |
What is Alloy 864?
Alloy 864 (S35135) is a nickel-iron-chromium superaustenitic alloy engineered for high-temperature strength and resistance to carburizing and oxidizing atmospheres, used as an upgrade material in thermal processing equipment. Annealed properties are 290 MPa yield, 620 MPa tensile, 45 % elongation and 170 HB, with service to about 950 °C; forms include annealed and bright-annealed tube, hot-rolled annealed and cold-drawn bar, quarter-hard to full-hard cold-worked tube and stress-relieved product. Formability is high (score 78) for bellows and convoluted parts, but machining is slow and cost sits well above 321/347. S35140 is the nearest alternative when a higher temperature ceiling is needed. Alloy 864 has a density of 7.94 g/cm³ (0.287 lb/in³), heavier than 78% of stainless steel grades. It melts at 1,355°C (2,471 °F). Alloy 864 has a yield strength of 290 MPa (42.1 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 72% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 197 GPa (28.6 Msi).
What is Alloy 864 used for?
- pyrolysis furnace tubing
- high-temperature fixtures
- radiant coils
- carburizing furnace hardware
Advantages
- Forms and bends easily — 78/100, better than 90% of stainless steel grades
- High service temperature — 950°C (1,742 °F), better than 86% of stainless steel grades
- Ductile — tolerates forming and impact — 45%, better than 76% of stainless steel grades
Limitations
- Poor heat conductor — 11.5 W/m·K (6.64 BTU/hr·ft·°F), worse than 97% of stainless steel grades
- High embodied carbon — 7 kg CO₂/kg, worse than 96% of stainless steel grades
- Low electrical conductivity — 1.7 % IACS, worse than 93% of stainless steel grades
Alloy 864 properties
Typical room-temperature values for Alloy 864-Annealed; bars are the position among stainless steel grades.
Physical3
Alloy 864 has a density of 7.94 g/cm³ (0.287 lb/in³), heavier than 78% of stainless steel grades. It melts at 1,355°C (2,471 °F).
Mechanical14
Alloy 864 has a yield strength of 290 MPa (42.1 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 72% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 197 GPa (28.6 Msi).
Thermal5
Alloy 864 is rated for continuous service to 950°C (1,742 °F). It conducts heat at 11.5 W/m·K (6.64 BTU/hr·ft·°F), worse than 97% of stainless steel grades. Thermal expansion is 14.4 µm/m·K (8 µin/in·°F).
Electrical3
Alloy 864 conducts electricity at 1.7 % IACS, worse than 93% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (58/100), worse than 62% of stainless steel grades.
Sustainability4
Producing a kilogram of Alloy 864 takes about 95 MJ of energy and emits 7 kg of CO₂ — more than 96% of stainless steel grades. Typical recycled content is 35%.
Manufacturability6
Alloy 864's machinability is poor (28/100, worse than 79% of stainless steel grades); weldability very good (75/100); formability very good (78/100).
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. Alloy 864 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Alloy 864
Is Alloy 864 easy to machine?
Machine like a Ni-Fe-Cr heat-resisting alloy: rigid setup, sharp positive-rake carbide, low speed / heavy positive feed to cut under the work-hardened layer, flood coolant, avoid dwelling.
Can Alloy 864 be welded?
Readily joined by GTAW/GMAW/PAW with matching or Ni-base filler (e.g. ERNiCrMo-3 / 82-type); keep interpass temperature low, no preheat required, no post-weld heat treatment normally needed.
Can Alloy 864 be formed, bent or molded?
Excellent cold formability for bellows, convolutions and deep-drawn parts; work-hardening rate is high, so plan intermediate solution anneals (~1065–1120 °C, rapid cool) for severe forming.
Alloy 864 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 |
|---|---|---|
| Niprimary austenite stabilizer, gives chloride-SCC and carburization resistance | 33 – 35 | 34 |
| Croxidation/scale resistance | 20 – 22 | 21 |
| Mopitting resistance and high-temperature strength | 3.5 – 4.5 | 4.2 |
| Ticarbide stabilization | 0.15 – 0.6 | 0.4 |
| Si | ≤ 1 | 0.5 |
| Mn | ≤ 1 | 0.5 |
| C | ≤ 0.05 | 0.03 |
| S | ≤ 0.02 | |
| P | ≤ 0.03 | |
| Febalance, approx. 37–40 % | balance |
What surface finishes work on Alloy 864?
Pickle/passivate after hot work to restore the chromia film; takes a good mechanical and electropolished finish; no anodizing — plating or paint is rarely needed for exhaust/furnace service.
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 Alloy 864 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S35135
How much does Alloy 864 cost?
Alloy 864 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.
Alloy 864 — frequently asked
What is Alloy 864 used for?
Alloy 864 is typically used for pyrolysis furnace tubing, high-temperature fixtures, radiant coils and carburizing furnace hardware. In short: best-forming heat-resistant superaustenitic; carburization-resistant furnace alloy; upgrade over 321/347.
What is the yield strength of Alloy 864?
Alloy 864 has a typical yield strength of 290 MPa (42.1 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 72% of stainless steel grades. Strength varies by condition: see the 7 listed tempers.
Is Alloy 864 easy to machine?
Not especially — machinability is rated poor (28/100, worse than 79% of stainless steel grades). Machine like a Ni-Fe-Cr heat-resisting alloy: rigid setup, sharp positive-rake carbide, low speed / heavy positive feed to cut under the work-hardened layer, flood coolant, avoid dwelling.
Can Alloy 864 be welded?
Yes — weldability is rated very good (75/100). Readily joined by GTAW/GMAW/PAW with matching or Ni-base filler (e.g. ERNiCrMo-3 / 82-type); keep interpass temperature low, no preheat required, no post-weld heat treatment normally needed.
What surface finishes work on Alloy 864?
Pickle/passivate after hot work to restore the chromia film; takes a good mechanical and electropolished finish; no anodizing — plating or paint is rarely needed for exhaust/furnace service.
Can Alloy 864 be formed, bent or molded?
Excellent cold formability for bellows, convolutions and deep-drawn parts; work-hardening rate is high, so plan intermediate solution anneals (~1065–1120 °C, rapid cool) for severe forming.
What is the maximum service temperature of Alloy 864?
Alloy 864 is rated for continuous use to about 950°C (1,742 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Alloy 864 Annealed and Alloy 864 CW-FH?
Annealed is the default condition — standard stocked condition: maximum ductility for bellows/flex-tube forming and best corrosion/oxidation performance. CW-FH: maximum strength condition for wire, springs and braid used in exhaust flex couplings; very limited ductility. Yield strength is 290 MPa in Annealed versus 965 MPa in CW-FH.
How much does Alloy 864 cost?
Alloy 864 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
- INCOLOY alloy 864 (UNS S35135) technical bulletin — Special Metals Corporation (2004)
- ASTM B815 / ASTM A1058-family test practice and UNS S35135 registration — ASTM International / SAE-ASTM UNS (2020)
- ASM Handbook Vol. 1: Properties and Selection — Heat-Resistant Fe-Ni-Cr Alloys — ASM International (1990)
- ASM Specialty Handbook: Heat-Resistant Materials — ASM International (1997)
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.