Alloy 21 is a low-carbon (0.20% max) cobalt-chromium-molybdenum alloy offering an exceptional balance of toughness, corrosion resistance, and high-temperature strength. Originally developed as one of the first biocompatible materials for hip implants and dental prosthetics, it also demonstrates proven performance in jet engine components and critical industrial applications. With good impact resistance and resistance to cavitation erosion, this alloy is widely used for valve trim in petrochemical service, hot stamping dies, and components requiring both mechanical toughness and corrosion protection .
1. Product Specifications & Physical DataZYTC Alloy supplies UNS R30021 in various forms for applications requiring verified impact resistance and corrosion properties. Available Forms: Castings, hardfacing rods, powder, wire, and machined components . Specifications: UNS R30021, AMS 5388 (castings), ASTM F75 (medical castings), AWS A5.21 (ERCoCr-E) .
| Chemical Composition (Weight %) | UNS R30021 Specification |
|---|
| Cobalt (Co) | Balance | | Chromium (Cr) | 27.0 - 29.0 | | Molybdenum (Mo) | 5.0 - 6.0 | | Nickel (Ni) | 2.0 - 3.0 | | Carbon (C) | 0.20 max. | | Iron (Fe) | 2.0 max. | | Silicon (Si) | 1.0 max. | | Manganese (Mn) | 1.0 max. |
| Physical Properties | Metric | Imperial |
|---|
| Density | 8.33 g/cm³ | 0.301 lb/in³ | | Melting Range | 1285 - 1360°C | 2345 - 2480°F | | Thermal Conductivity | 11.9 W/m·K | 82.6 BTU·in/hr·ft²·°F | | Modulus of Elasticity | 205 - 210 GPa | 29.7 - 30.5 × 10⁶ psi |
| Mechanical Properties | Metric | Imperial |
|---|
| Tensile Strength | 850 - 900 MPa | 123 - 130 ksi | | Yield Strength | 500 - 600 MPa | 72.5 - 87 ksi | | Hardness | 45 - 50 HRC | 45 - 50 HRC | | Elongation | ~10% | ~10% | | Creep Strength | Good at elevated temperatures | Good at elevated temperatures |
2. Fabrication & Material ComparisonHeat Treatment: Solution treat 1200-1240°C (2190-2265°F), rapid quench; age 700-1150°C (1290-2100°F) for optimized high-temperature strength . Casting: Excellent fluidity for complex castings; produces sound metallurgical structure . Hardfacing: Can be applied via PTA welding, laser cladding, and spray and fuse methods. Oxyacetylene deposition not recommended . Machining: Can be machined with carbide tooling in annealed condition; best finished by grinding due to work-hardening characteristics . Material Comparison: vs. Stellite 6: Lower carbon (0.20% vs. 1.2%) provides superior impact resistance and toughness; good corrosion resistance . vs. Stellite 12: Better impact resistance; lower wear resistance due to absence of tungsten carbides .
3. ApplicationsMedical: Hip implants, dental prosthetics, surgical instruments (ASTM F75) Petrochemical: Valve trim, seats, stems for corrosive service Power Generation: Turbine components, steam path hardware Industrial Tooling: Forging dies, hot stamping dies, extrusion tooling Pump Components: Impellers, wear rings, sleeves for cavitation service Aerospace: Jet engine components, bearing surfaces
Contact ZYTC Alloy for certified Alloy 21 (UNS R30021) materials with complete traceability, ASTM/AMS specifications, technical datasheets, and competitive pricing on standard sizes or custom-fabricated components. Email: daisy@zytcsteel.com WhatsApp/WeChat: +86 17335753350 |
