Refractory Metal Cb-752-SR (Stress relieved)
Heat-treated state
UNS R04351
Pick when higher room- and mid-temperature strength is needed but some cold-work ductility must be retained.
Values for the SR condition
Other Cb-752 tempers and conditions
Cb-752 is listed in 3 conditions; see the grade overview at Cb-752.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
RXDefault Recrystallized | Standard stocked condition: fully annealed (~1200–1315 °C vacuum), maximum ductility for forming, spinning and welding. | 310 | 450 | 25 | 170 HB | 7.2 % IACS |
SRThis page Stress relieved | Pick when higher room- and mid-temperature strength is needed but some cold-work ductility must be retained. | 470 | 550 | 18 | 18 HRC | 7 % IACS |
Cold worked | Highest room-temperature strength and hardness; use for thin foil, springs and parts not exposed to recrystallization temperatures. | 620 | 690 | 8 | 24 HRC | 6.8 % IACS |
What is Cb-752-SR?
Cb-752-SR is Cb-752 heat treated to SR — pick when higher room- and mid-temperature strength is needed but some cold-work ductility must be retained. Cb-752-SR has a yield strength of 470 MPa (68.2 ksi) and a tensile strength of 550 MPa (79.8 ksi) — stronger than 70% of refractory metal grades. Elongation at break is 18% and the elastic modulus is 110 GPa (16 Msi). Cb-752-SR has a density of 9.03 g/cm³ (0.326 lb/in³), heavier than 57% of refractory metal grades. It melts at 2,470°C (4,478 °F). RX is the default condition FabDigit quotes; SR is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 70 MPa·√m (63.7 ksi·√in), better than 84% of refractory metal grades
Cb-752-SR properties
Typical room-temperature values for Cb-752-SR; 23 are specific to this condition. Other listed values are Cb-752 reference data and may not represent this condition. Bars are the position among refractory metal grades.
Physical3
Cb-752-SR has a density of 9.03 g/cm³ (0.326 lb/in³), heavier than 57% of refractory metal grades. It melts at 2,470°C (4,478 °F).
Mechanical16
Cb-752-SR has a yield strength of 470 MPa (68.2 ksi) and a tensile strength of 550 MPa (79.8 ksi) — stronger than 70% of refractory metal grades. Elongation at break is 18% and the elastic modulus is 110 GPa (16 Msi).
Thermal6
Cb-752-SR is rated for continuous service to 1,200°C (2,192 °F). It conducts heat at 39 W/m·K (22.5 BTU/hr·ft·°F), worse than 56% of refractory metal grades. Thermal expansion is 7.1 µm/m·K (3.94 µin/in·°F).
Electrical3
Cb-752-SR conducts electricity at 7 % IACS, better than 54% of refractory metal grades.
Chemical & Environmental2
Corrosion resistance is very good (72/100), worse than 58% of refractory metal grades.
Sustainability3
Producing a kilogram of Cb-752-SR takes about 950 MJ of energy and emits 62 kg of CO₂ — less than 55% of refractory metal grades. Typical recycled content is 25%.
Manufacturability7
Cb-752-SR's machinability is poor (34/100, better than 73% of refractory metal grades); weldability good (68/100); formability good (55/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Cb-752-SR
Is Cb-752 easy to machine?
Machine like a gummy austenitic alloy: sharp, positive-rake carbide or HSS tools, slow speed, heavy feed, flood coolant (chlorinated oil) to avoid galling and built-up edge; degrease thoroughly before any heat treatment.
Can Cb-752 be welded?
GTAW in a high-purity argon chamber or EB welding in vacuum; any air or hydrocarbon pickup embrittles the weld, so joints must be spotlessly clean and post-weld vacuum annealed if strength recovery is needed.
Can Cb-752 be formed, bent or molded?
Excellent cold formability in the annealed condition — spun, deep drawn and roll-formed into nozzle skirts; hot work only in vacuum or inert atmosphere with molybdenum-coated or canned tooling.
What surface finishes work on Cb-752?
Chemically mill/pickle in HF-HNO₃ mixtures, then apply a fused silicide (R512E) or aluminide coating for oxidizing high-temperature service; electropolishing gives the best surface for coating adhesion.
Cb-752 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 |
|---|---|---|
| Wprimary solid-solution strengthener | 9 – 11 | 10 |
| Zroxide/carbide former, raises creep strength | 2 – 3 | 2.5 |
| Taresidual | ≤ 0.5 | — |
| Hfresidual | ≤ 0.1 | — |
| Fe | ≤ 0.01 | — |
| Ti | ≤ 0.02 | — |
| C | ≤ 0.02 | — |
| Ointerstitial control critical for ductility | ≤ 0.02 | — |
| N | ≤ 0.01 | — |
| H | ≤ 0 | — |
| Nb | balance | — |
Cb-752-SR — frequently asked
What is Cb-752-SR used for?
Cb-752-SR is typically used for rocket nozzle extensions, re-entry vehicle leading edges and high-temperature aerospace sheet structures. In short: highly formable Nb-W-Zr sheet; legacy nozzle-skirt alloy; coating required above ambient service.
What is the yield strength of Cb-752-SR?
Cb-752-SR has a typical yield strength of 470 MPa (68.2 ksi) and a tensile strength of 550 MPa (79.8 ksi) — stronger than 70% of refractory metal grades. Strength varies by condition: see the 3 listed tempers.
Is Cb-752-SR easy to machine?
Not especially — machinability is rated poor (34/100, better than 73% of refractory metal grades). Machine like a gummy austenitic alloy: sharp, positive-rake carbide or HSS tools, slow speed, heavy feed, flood coolant (chlorinated oil) to avoid galling and built-up edge; degrease thoroughly before any heat treatment.
Can Cb-752-SR be welded?
Yes — weldability is rated good (68/100). GTAW in a high-purity argon chamber or EB welding in vacuum; any air or hydrocarbon pickup embrittles the weld, so joints must be spotlessly clean and post-weld vacuum annealed if strength recovery is needed.
What surface finishes work on Cb-752-SR?
Chemically mill/pickle in HF-HNO₃ mixtures, then apply a fused silicide (R512E) or aluminide coating for oxidizing high-temperature service; electropolishing gives the best surface for coating adhesion.
Can Cb-752-SR be formed, bent or molded?
Excellent cold formability in the annealed condition — spun, deep drawn and roll-formed into nozzle skirts; hot work only in vacuum or inert atmosphere with molybdenum-coated or canned tooling.
What is the maximum service temperature of Cb-752-SR?
Cb-752-SR is rated for continuous use to about 1,200°C (2,192 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Cb-752-RX and Cb-752-CW?
RX is the default condition — standard stocked condition: fully annealed (~1200–1315 °C vacuum), maximum ductility for forming, spinning and welding. CW: highest room-temperature strength and hardness; use for thin foil, springs and parts not exposed to recrystallization temperatures. Yield strength is 310 MPa in RX versus 620 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 — Niobium alloy property compilations (Cb-752, C-103, FS-85) — TMS / Battelle DMIC reports (1965)
- UNS R04351 alloy designation (Metals & Alloys in the Unified Numbering System) — SAE/ASTM (2017)
- Niobium alloy sheet, plate and bar datasheets — ATI / Wah Chang, Plansee (2022)
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.