Cobalt Alloys HY ST31 / Stellite 31 / UNS R30031 Product Introduction
Cobalt alloys such as HY ST31 (Stellite 31) and UNS R30031 are renowned for their exceptional resistance to wear, corrosion, and high temperatures. This article provides a comprehensive introduction to these alloys, covering their chemical composition, mechanical properties, performance at different temperatures, industry applications, shapes and sizes, production standards, welding and processing capabilities, advantages and disadvantages, and comparisons with similar alloys.
Chemical Composition
HY ST31 (Stellite 31) and UNS R30031 have a complex chemical composition designed to achieve their high-performance properties:
| Element | Composition (%) |
|---|---|
| Cobalt (Co) | 30.0 – 34.0 |
| Chromium (Cr) | 27.0 – 31.0 |
| Tungsten (W) | 12.0 – 15.0 |
| Nickel (Ni) | 3.0 – 5.0 |
| Iron (Fe) | 3.0 – 4.5 |
| Molybdenum (Mo) | 2.0 – 3.5 |
| Carbon (C) | 0.05 – 0.15 |
| Manganese (Mn) | 1.0 max |
| Silicon (Si) | 1.0 max |
| Phosphorus (P) | 0.04 max |
| Sulfur (S) | 0.04 max |
Mechanical Properties
HY ST31 (Stellite 31) and UNS R30031 exhibit excellent mechanical properties suitable for high-stress applications:
| Property | Value |
|---|---|
| Tensile Strength, ksi (MPa) | 135 (930) min |
| Yield Strength (0.2% offset), ksi (MPa) | 105 (725) min |
| Elongation (% in 2 inches) | 20 min |
| Hardness, Rockwell C (HRC) | 38 – 44 |
Performance Characteristics
These cobalt alloys offer outstanding performance in severe environments:
- Wear Resistance: Exceptional resistance to abrasion, erosion, and metal-to-metal wear, making them ideal for high-stress wear applications.
- Corrosion Resistance: Excellent resistance to oxidation and corrosion in high-temperature and corrosive environments, including acids and alkalis.
- High Temperature Strength: Maintains strength and hardness at elevated temperatures, up to approximately 1200°F (650°C).
Industry Applications
HY ST31 (Stellite 31) and UNS R30031 are utilized across various industries where durability and resistance to wear and corrosion are critical:
| Industry Sector | Applications |
|---|---|
| Aerospace | Turbine blades, combustion chambers, and high-temperature engine components. |
| Oil and Gas | Valves, pump components, and drilling equipment exposed to abrasive and corrosive fluids. |
| Medical | Surgical instruments, prosthetic devices, and biomedical implants requiring wear and corrosion resistance. |
Shapes and Sizes
These alloys are available in various forms and sizes to suit different applications:
- Forms: Sheets, plates, bars, tubes, and custom shapes.
- Sizes: Thickness ranging from 0.025 inches to 1.000 inches (0.64mm to 25.4mm), diameter ranging from 0.25 inches to 6.0 inches (6.35mm to 152.4mm).
Production Standards
HY ST31 (Stellite 31) and UNS R30031 conform to industry standards ensuring quality and reliability:
| Product Form | Shapes Available | Sizes Available | Production Standards |
|---|---|---|---|
| Bars/Rods | Round bars, square bars | Diameter: 0.25″ – 6.0″ (6.35mm – 152.4mm) | ASTM A732, AMS 5759 |
| Plates/Sheets | Plates, Sheets | Thickness: 0.025″ – 1.000″ (0.64mm – 25.4mm) | ASTM A732, AMS 5537 |
| Wires | Wires | Diameter: 0.010″ – 0.250″ (0.25mm – 6.35mm) | ASTM A580, AMS 5832 |
| Tubes/Pipes | Tubes, Pipes | OD: 0.250″ – 6.000″ (6.35mm – 152.4mm) | ASTM A732, AMS 5759 |
Welding and Processing
HY ST31 (Stellite 31) and UNS R30031 offer good weldability and machinability:
- Welding: Can be welded using standard methods such as TIG and MIG welding with appropriate preheating and post-weld heat treatment.
- Processing: Machinable using carbide tools, although care is needed due to their high hardness and toughness.
Advantages and Disadvantages
| Aspect | Details |
|---|---|
| Advantages | High wear resistance, excellent strength at elevated temperatures, good corrosion resistance, and versatility in various applications. |
| Disadvantages | Higher cost compared to conventional materials, requires expertise in handling due to their high strength and hardness. |
Similar Alloys
| Alloy Name | Comparison |
|---|---|
| Cobalt Alloy 6 | Higher cobalt content, offering superior wear resistance and hardness compared to HY ST31 and UNS R30031. |
Comparison of Similar Alloys
| Property/Feature | HY ST31 / UNS R30031 | Cobalt Alloy 6 |
|---|---|---|
| Cobalt Content (%) | 30.0 – 34.0 | 54.0 – 62.0 |
| Chromium Content (%) | 27.0 – 31.0 | 25.0 – 32.0 |
| Tungsten Content (%) | 12.0 – 15.0 | 8.0 – 10.0 |
| Hardness, Rockwell C (HRC) | 38 – 44 | 48 – 55 |
| Applications | Aerospace, Oil & Gas, Medical | Industrial tools, wear components |
This detailed article provides a comprehensive introduction to HY ST31 (Stellite 31) and UNS R30031, highlighting their chemical composition, mechanical properties, performance characteristics, industry applications, available forms and sizes, production standards, welding and processing capabilities, as well as advantages, disadvantages, and comparisons with similar alloys. Engineers and professionals seeking durable materials for high-wear and corrosion-resistant applications will find this information valuable for selecting the appropriate alloy to meet their specific needs.