Refractory Metal FS-85-REX (Recrystallized Annealed)
Heat-treated state · default condition
UNS R04366
Standard stocked condition for sheet, plate and bar — best ductility, formability and weldability, used for creep-limited high-temperature service.
Values for the REX condition
Other FS-85 tempers and conditions
FS-85 is listed in 6 conditions; see the grade overview at FS-85.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As cast | Ingot condition supplied for remelt or subsequent conversion — coarse grain, lower strength, not used for finished structural parts. | 400 | 520 | 25 | 190 HB | 3.5 % IACS |
As-welded deposit | Property basis for joint design; FS-85 welds stay ductile if oxygen/nitrogen pickup is controlled in a high-purity chamber. | 450 | 560 | 15 | 214 HB | 3.4 % IACS |
REXDefaultThis page Recrystallized Annealed | Standard stocked condition for sheet, plate and bar — best ductility, formability and weldability, used for creep-limited high-temperature service. | 480 | 585 | 22 | 18 HRC | 3.4 % IACS |
Hot Worked / As-Forged bar and plate | Mill condition for heavy bar, billet and forgings before final vacuum anneal; strength between annealed and cold-worked. | 550 | 660 | 19 | 21 HRC | 3.3 % IACS |
Stress relieved | Pick when moderately higher room-temperature strength is wanted while removing cold-work residual stress before welding or machining. | 630 | 720 | 15 | 24 HRC | 3.4 % IACS |
Cold worked | Highest room-temperature strength for foil, thin sheet and wire, but limited ductility and it recrystallizes above ~1250 °C. | 830 | 900 | 6 | 32 HRC | 3.3 % IACS |
What is FS-85-REX?
FS-85-REX is FS-85 heat treated to REX — standard stocked condition for sheet, plate and bar — best ductility, formability and weldability, used for creep-limited high-temperature service. FS-85-REX has a yield strength of 480 MPa (69.6 ksi) and a tensile strength of 585 MPa (84.8 ksi) — stronger than 72% of refractory metal grades. Elongation at break is 22% and the elastic modulus is 138 GPa (20 Msi). FS-85-REX has a density of 10.6 g/cm³ (0.383 lb/in³), heavier than 71% of refractory metal grades. It melts at 2,590°C (4,694 °F).
Advantages
- Tough — resists crack growth — 80 MPa·√m (72.8 ksi·√in), better than 91% of refractory metal grades
- High service temperature — 1,500°C (2,732 °F), better than 86% of refractory metal grades
- Forms and bends easily — 70/100, better than 75% of refractory metal grades
FS-85-REX properties
Typical room-temperature values for FS-85-REX; 23 are specific to this condition. Other listed values are FS-85 reference data and may not represent this condition. Bars are the position among refractory metal grades.
Physical3
FS-85-REX has a density of 10.6 g/cm³ (0.383 lb/in³), heavier than 71% of refractory metal grades. It melts at 2,590°C (4,694 °F).
Mechanical17
FS-85-REX has a yield strength of 480 MPa (69.6 ksi) and a tensile strength of 585 MPa (84.8 ksi) — stronger than 72% of refractory metal grades. Elongation at break is 22% and the elastic modulus is 138 GPa (20 Msi).
Thermal5
FS-85-REX is rated for continuous service to 1,500°C (2,732 °F). It conducts heat at 40 W/m·K (23.1 BTU/hr·ft·°F), worse than 55% of refractory metal grades. Thermal expansion is 7 µm/m·K (3.89 µin/in·°F).
Electrical3
FS-85-REX conducts electricity at 3.4 % IACS, worse than 72% of refractory metal grades.
Chemical & Environmental3
Corrosion resistance is very good (72/100), worse than 58% of refractory metal grades.
Sustainability3
Producing a kilogram of FS-85-REX takes about 900 MJ of energy and emits 60 kg of CO₂ — less than 59% of refractory metal grades. Typical recycled content is 25%.
Manufacturability7
FS-85-REX's machinability is poor (25/100, worse than 65% of refractory metal grades); weldability very good (70/100); formability very good (70/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with FS-85-REX
Is FS-85 easy to machine?
Machine like a gummy refractory metal: sharp uncoated carbide, positive rake, slow speed, heavy flood coolant, avoid dwell to prevent galling and work hardening.
Can FS-85 be welded?
Electron-beam or GTAW inside a high-purity argon chamber or vacuum; any oxygen/nitrogen pickup embrittles the weld, so joints must be spotlessly clean and back-shielded.
Can FS-85 be formed, bent or molded?
Cold rollable and formable at room temperature with generous bend radii and intermediate vacuum anneals; heavy sections are forged/extruded hot at 1200–1400 °C with cladding or glass lubricant.
What surface finishes work on FS-85?
Chemical etch (HF-HNO3) or electropolish to remove smeared metal; for use in air above ~450 °C apply an R512E-type silicide diffusion coating.
FS-85 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 |
|---|---|---|
| Taprimary solid-solution strengthener | 26 – 29 | 28 |
| W | 10 – 11.5 | 10.5 |
| Zrgetters O/C, forms fine ZrO2/ZrC dispersion | 0.7 – 1.3 | 1 |
| Cimpurity limit | ≤ 0.03 | 0.01 |
| Oimpurity limit | ≤ 0.02 | 0.01 |
| Nimpurity limit | ≤ 0.01 | 0 |
| Himpurity limit | ≤ 0 | 5×10⁻⁴ |
| Feimpurity limit | ≤ 0.01 | — |
| Nbbalance, ~60 wt % | balance | — |
FS-85-REX — frequently asked
What is FS-85-REX used for?
FS-85-REX is typically used for rocket thruster components, high-temperature aerospace sheet parts, heat shields and nuclear propulsion hardware. In short: fabricable refractory sheet alloy; 1500 °C service capability; silicide coating required.
What is the yield strength of FS-85-REX?
FS-85-REX has a typical yield strength of 480 MPa (69.6 ksi) and a tensile strength of 585 MPa (84.8 ksi) — stronger than 72% of refractory metal grades. Strength varies by condition: see the 6 listed tempers.
Is FS-85-REX easy to machine?
Not especially — machinability is rated poor (25/100, worse than 65% of refractory metal grades). Machine like a gummy refractory metal: sharp uncoated carbide, positive rake, slow speed, heavy flood coolant, avoid dwell to prevent galling and work hardening.
Can FS-85-REX be welded?
Yes — weldability is rated very good (70/100). Electron-beam or GTAW inside a high-purity argon chamber or vacuum; any oxygen/nitrogen pickup embrittles the weld, so joints must be spotlessly clean and back-shielded.
What surface finishes work on FS-85-REX?
Chemical etch (HF-HNO3) or electropolish to remove smeared metal; for use in air above ~450 °C apply an R512E-type silicide diffusion coating.
Can FS-85-REX be formed, bent or molded?
Cold rollable and formable at room temperature with generous bend radii and intermediate vacuum anneals; heavy sections are forged/extruded hot at 1200–1400 °C with cladding or glass lubricant.
What is the maximum service temperature of FS-85-REX?
FS-85-REX is rated for continuous use to about 1,500°C (2,732 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between FS-85-REX and FS-85-CW?
REX is the default condition — standard stocked condition for sheet, plate and bar — best ductility, formability and weldability, used for creep-limited high-temperature service. CW: highest room-temperature strength for foil, thin sheet and wire, but limited ductility and it recrystallizes above ~1250 °C. Yield strength is 480 MPa in REX versus 830 MPa in CW.
Sources
- ASM Handbook, Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (refractory metals section) — ASM International (1990)
- Refractory Metals and Alloys — property compilations for Nb-base alloys (C-103, Cb-752, FS-85) — Plenum / TMS literature (1988)
- Niobium and tantalum alloy mill product data (FS-85, C-103) — ATI Wah Chang (2015)
- ASTM B654 / B655 — Niobium-alloy strip, sheet, plate and bar (related product specifications) — ASTM International (2020)
- NASA technical reports on FS-85 for space power and thermal-structural applications — NASA NTRS (2010)
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.