Refractory Metal Cb-752
UNS R04351
Cb-752 (UNS R04351) is an older-generation niobium–tungsten–zirconium alloy with good high-temperature strength, widely used for rocket nozzle skirts and re-entry structures before C-103 became the industry standard.
Reference datasheet — Cb-752 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 RX condition
Cb-752 tempers and conditions
Cb-752 is supplied in 3 conditions, soft to hard. RX is the default FabDigit quotes; the values on this page are for it.
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 |
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 |
Supply forms, finishes and certifications
Ways Cb-752 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
RX+R512E | Recrystallized + fused silicide coating | Surface finish |
What is Cb-752?
Cb-752 (UNS R04351) is an older-generation niobium–tungsten–zirconium alloy with good high-temperature strength, widely used for rocket nozzle skirts and re-entry structures before C-103 became the industry standard. Recrystallised sheet gives 310 MPa yield, 450 MPa tensile and 25 % elongation with a formability score of 75, so it spins, deep draws and roll-forms into thin-wall nozzle extensions for service to about 1400 °C. Bare material must run with a fused silicide coating such as R512E in oxidising service, and availability is limited; C-103 is the usual substitute today. Cb-752 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). Cb-752 has a yield strength of 310 MPa (45 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 55% of refractory metal grades. Elongation at break is 25% and the elastic modulus is 110 GPa (16 Msi).
What is Cb-752 used for?
- rocket nozzle extensions
- re-entry vehicle leading edges
- high-temperature aerospace sheet structures
Advantages
- Tough — resists crack growth — 70 MPa·√m (63.7 ksi·√in), better than 84% of refractory metal grades
- High service temperature — 1,400°C (2,552 °F), better than 81% of refractory metal grades
- Forms and bends easily — 75/100, better than 81% of refractory metal grades
Cb-752 properties
Typical room-temperature values for Cb-752-RX; bars are the position among refractory metal grades.
Physical3
Cb-752 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 has a yield strength of 310 MPa (45 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 55% of refractory metal grades. Elongation at break is 25% and the elastic modulus is 110 GPa (16 Msi).
Thermal6
Cb-752 is rated for continuous service to 1,400°C (2,552 °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 7.1 µm/m·K (3.94 µin/in·°F).
Electrical3
Cb-752 conducts electricity at 7.2 % IACS, better than 55% 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 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's machinability is poor (30/100, better than 54% of refractory metal grades); weldability very good (70/100); formability very good (75/100).
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 refractory metal family
Yield strength against density for every refractory metal grade FabDigit runs. Cb-752 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Cb-752
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.
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 |
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.
Equivalent designations
Standards and trade names that resolve to Refractory Metal Cb-752 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- R04351
How much does Cb-752 cost?
Cb-752 is a high-cost refractory metal ($$$$), 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.
Cb-752 — frequently asked
What is Cb-752 used for?
Cb-752 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?
Cb-752 has a typical yield strength of 310 MPa (45 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 55% of refractory metal grades. Strength varies by condition: see the 3 listed tempers.
Is Cb-752 easy to machine?
Not especially — machinability is rated poor (30/100, better than 54% 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 be welded?
Yes — weldability is rated very good (70/100). 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?
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 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?
Cb-752 is rated for continuous use to about 1,400°C (2,552 °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.
How much does Cb-752 cost?
Cb-752 is a high-cost refractory metal ($$$$), 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. 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; 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.