Cobalt Alloy 6b,Stellite 6b ,UNS R30016

Cobalt Alloy 6b,Stellite 6b Wire,UNS R30016

Cobalt Alloy 6b (Stellite 6b Wire, UNS R30016) - Introduction with Composition, Properties, Applications and Product Forms

Cobalt Alloy 6b, commercially known as Stellite 6b and designated by UNS R30016, is a cobalt-chromium-tungsten alloy renowned for its exceptional wear resistance, high-temperature strength, and corrosion resistance. This hardfacing alloy is specifically engineered to withstand extreme conditions, including heavy friction, elevated temperatures, and aggressive chemical environments, making it a cornerstone material in industrial applications requiring long-term durability. It is available in a comprehensive range of forms to meet diverse industrial needs, including Bar (Round bar, Flat bar), Ribbon, Wire, Rods, Tube, Pipe, Foil, Plate, Sheet, Strip, and Forging Stock. Stellite 6b Wire, in particular, is valued for its uniform hardness, ductility, and precision, making it ideal for hardfacing, welding, and intricate components in aerospace, energy, and manufacturing industries. Below is a detailed overview of its chemical composition, key properties, practical applications, and available product forms.

Chemical Composition

The precisely balanced chemical composition of Cobalt Alloy 6b (Stellite 6b, UNS R30016) is the foundation of its exceptional wear resistance, high-temperature performance, and corrosion resistance. The typical composition (by weight) is as follows:

Cobalt (Co): 50-55% (the primary element, providing high-temperature stability and forming the alloy’s matrix)

Chromium (Cr): 27-30% (enhances corrosion and oxidation resistance, forming a protective oxide layer at high temperatures)

Tungsten (W): 4-6% (contributes to wear resistance through the formation of hard carbides)

Nickel (Ni): 1-3% (improves ductility and toughness without compromising hardness)

Iron (Fe): ≤ 3% (minimized to maintain corrosion resistance and high-temperature properties)

Carbon (C): 1.0-1.4% (forms hard carbides with tungsten and chromium, critical for wear resistance)

Silicon (Si): ≤ 1% (aids in deoxidation during manufacturing and improves weldability)

Manganese (Mn): ≤ 1% (enhances hot workability and controls sulfur content)

Other elements (e.g., molybdenum, vanadium): ≤ 1% (trace additions to refine microstructure and properties)

This carefully engineered composition, with its blend of cobalt, chromium, and tungsten carbides, delivers the alloy’s signature hardness, wear resistance, and stability at elevated temperatures—key to its performance in extreme industrial environments.

Key Properties

Cobalt Alloy 6b (Stellite 6b Wire, UNS R30016) and its various forms exhibit extraordinary properties that make them indispensable in high-wear, high-temperature applications:

Mechanical Properties (as-cast or welded condition):

Hardness: 38-44 HRC (Rockwell hardness, reflecting exceptional wear resistance)

Tensile strength: 900-1100 MPa (130,500-159,500 psi)

Yield strength (0.2% offset): 500-650 MPa (72,500-94,300 psi)

Elongation (in 50 mm): 4-8% (moderate ductility, enabling limited forming and welding)

Impact toughness (Charpy V-notch): 10-15 J (7.4-11.1 ft-lb) at room temperature (sufficient toughness for wear applications)

High-Temperature Properties:

Continuous service temperature: Up to 815°C (1500°F) (maintains strength and oxidation resistance)

Oxidation resistance: Excellent resistance to oxidation and scaling at temperatures up to 980°C (1800°F), due to chromium oxide layer formation

Hot hardness: Retains hardness (>30 HRC) at temperatures up to 650°C (1200°F), critical for high-temperature wear applications

Corrosion Resistance:

General corrosion: Good resistance to atmospheric corrosion, freshwater, and mild acids

Pitting and crevice corrosion: Resistant to pitting in chloride environments, outperforming many stainless steels

Chemical resistance: Withstands exposure to oils, fuels, and industrial chemicals, making it suitable for harsh environments

Physical Properties:

Density: 8.5-8.7 g/cm³ (0.307-0.314 lb/in³)

Thermal conductivity: 25-28 W/(m·K) at 20°C (68°F)

Coefficient of thermal expansion: 13-15 μm/(m·K) (20-100°C)

Modulus of elasticity: 210-220 GPa (30,500-31,900 ksi) at room temperature

Melting point: 1260-1350°C (2300-2460°F)

Product Forms

Cobalt Alloy 6b (Stellite 6b, UNS R30016) is manufactured in a diverse range of forms to accommodate specialized high-wear and high-temperature applications:

Bar: Available as Round bar (diameters from 10 mm to 200 mm) and Flat bar (thickness 5 mm to 100 mm, width 20 mm to 500 mm), ideal for machining into wear-resistant components such as valves, bushings, and cutting tools.

Ribbon: Thin, flat strips (thickness 0.1 mm to 1 mm, width 5 mm to 100 mm) used in hardfacing, electrical contacts, and high-temperature seals.

Wire: Stellite 6b Wire (diameters 0.8 mm to 6 mm) is widely used for hardfacing via welding (MIG, TIG, or oxy-fuel), as well as for manufacturing precision springs and brushes in high-wear environments.

Rods: Solid cylindrical rods (diameters 3 mm to 50 mm) used for gas tungsten arc welding (GTAW) hardfacing, as well as for fabricating small wear components.

Tube and Pipe: Hollow forms (outer diameter 6 mm to 100 mm, wall thickness 1 mm to 10 mm) for high-temperature fluid handling, such as in chemical processing and energy systems.

Foil: Ultra-thin sheets (thickness 0.02 mm to 0.1 mm) used in high-temperature gaskets, electrical contacts, and thin wear-resistant coatings.

Plate and Sheet: Flat forms (plate: thickness 3 mm to 50 mm; sheet: 0.3 mm to 3 mm) for fabricating wear plates, valve seats, and heat-resistant structural components.

Strip: Narrow, flat strips (thickness 0.1 mm to 2 mm, width 3 mm to 50 mm) for precision components such as saw blades, seal rings, and electrical contacts.

Forging Stock: Billets and ingots for hot forging into complex shapes, such as turbine components, valve bodies, and heavy machinery parts.

Applications

The exceptional wear resistance, high-temperature strength, and corrosion resistance of Cobalt Alloy 6b (Stellite 6b Wire, UNS R30016) across its various forms make it a critical material in industries requiring durability under extreme conditions:

Aerospace and Aviation:

Turbine components: Wear-resistant coatings and parts (from wire, plate, and forging stock) for jet engine turbine blades, vanes, and shafts, withstanding high temperatures and friction.

Landing gear: Hardfaced surfaces (via wire and rod) for landing gear components, reducing wear from repeated takeoffs and landings.

Valves and actuators: Valve seats, stems, and seals (from bar and sheet) resisting high-temperature fuels and lubricants.

Energy and Power Generation:

Gas and steam turbines: Hardfaced components (from wire, plate, and forging stock) for turbine blades, nozzles, and seals, enduring high temperatures and particulate erosion.

Oil and gas drilling: Wear-resistant parts (from bar, rod, and tube) for drill bits, valves, and pumps, withstanding abrasive drilling fluids and high pressures.

Nuclear power: Corrosion-resistant components (from plate and tube) for coolant systems, resisting radiation and chemical degradation.

Manufacturing and Machinery:

Metalworking: Cutting tools, dies, and rolls (from bar and plate) for machining and forming hard metals, offering longer service life than conventional steels.

Mining equipment: Wear plates, conveyor components, and crusher parts (from plate and forging stock) resisting abrasion from ore and rock.

Printing and paper machinery: Doctor blades, rollers, and seals (from strip and ribbon) withstanding friction and chemical exposure from inks and paper.

Chemical Processing and Petrochemicals:

Valves and pumps: Valve seats, balls, and impellers (from bar and forging stock) resisting corrosion from acids, solvents, and hydrocarbons.

Reactor components: Liners and heat exchangers (from plate and tube) withstanding high temperatures and aggressive chemicals.

Pipelines: Hardfaced welds (using wire and rod) for pipeline joints, preventing erosion from abrasive fluids.

Medical and Specialized Applications:

Medical devices: Surgical tools and implants (from bar and wire) offering wear resistance and biocompatibility.

Automotive racing: Engine valves, piston rings, and exhaust components (from bar and forging stock) withstanding high temperatures and friction.

Waste incineration: Heat-resistant and corrosion-resistant components (from plate and tube) for incinerator liners and exhaust systems.

Specialized Applications by Form:

Wire: Hardfacing via welding, manufacturing brushes for deburring, and precision springs in high-wear machinery.

Bar/Plate: Wear-resistant components (valves, bushings, cutting tools) and structural parts in high-temperature systems.

Rod/Tube: Welding rods for hardfacing, and tubing for high-temperature fluid handling in chemical processing.

Strip/Ribbon: Electrical contacts, seal rings, and doctor blades requiring wear and corrosion resistance.

In summary, Cobalt Alloy 6b (Stellite 6b Wire, UNS R30016) — available in forms from Bar and Wire to Plate and Forging Stock — delivers exceptional wear resistance, high-temperature strength, and corrosion resistance. Its diverse product forms enable tailored solutions across aerospace, energy, manufacturing, and chemical sectors, establishing it as a critical material in applications requiring durability under extreme conditions.

Packing of Standard Packing: 

Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 1386 gallon liquid totes Special package is available on request.