Products Features
Excellent Hardness and Wear Resistance
Stellite 8 forms numerous hard carbides of the M₇C₃ and M₆C types, uniformly distributed within a cobalt-based solid solution matrix. Typical cast or weld-deposited hardness ranges from HRC 45-55 (approximately HV 450-600), offering significantly better resistance to abrasive and erosive wear compared to Stellite 6, while maintaining superior impact and thermal crack resistance over Stellite 1 and 4.
Superior Hot Hardness and Oxidation Resistance
Stellite 8 retains approximately 38 HRC at 600°C, about 30 HRC at 760°C (1400°F), and around 22 HRC at 870°C (1600°F). Its high chromium content promotes the formation of a dense Cr₂O₃ oxide film on the surface. After exposure to air at 800°C for 1000 hours, oxidation weight gain remains below 1 mg/cm², providing far better oxidation resistance than tool steels and iron-based wear-resistant materials. This makes it suitable for high-temperature applications such as hot extrusion, hot shearing, and gas turbines.
Good Corrosion Resistance
With approximately 30% chromium content, Stellite 8 exhibits good corrosion resistance in oxidizing acids (e.g., nitric acid), moderately concentrated non-oxidizing acids (e.g., ≤50% sulfuric acid), and alkaline solutions. In seawater and chloride environments, it primarily shows pitting corrosion rather than uniform corrosion, with outstanding corrosion resistance in high-temperature atmospheres containing sulfur and chlorine.
Favorable Machinability and Weldability
Stellite 8 offers better weldability and machinability than high-carbon grades (e.g., Stellite 1, 4). It can be deposited using PTA, TIG, and oxy-acetylene welding methods. Preheating to 400-550°C and slow cooling after welding are recommended to reduce the risk of hot cracking. Limited machining is possible in annealed condition, with final finishing typically recommended via grinding or electrical discharge machining (EDM).
Technical Specifications
Chemical Composition
|
Element |
Standard Requirements |
Notes |
|
Co |
Remaining quantity |
Matrix elements that provide high-temperature strength, thermal stability, toughness, and inherent corrosion resistance |
|
Cr |
28.0 - 32.0% |
Form a dense Cr₂O₃ protective film, providing oxidation and corrosion resistance, and is also a main component of hard carbides |
|
W |
8.0 - 10.0% |
Provide solid solution strengthening, form hard and wear-resistant carbides with carbon, and enhance high-temperature hardness and creep resistance |
|
C |
1.5 - 2.5% |
Forming a large amount of high-hardness carbides (M₇C₃, M₆C) with chromium and tungsten, which are the core source of wear resistance. |
|
Fe |
≤ 3.0% |
Strict control to ensure purity and microstructural stability |
|
Ni |
≤ 3.0% |
Strictly control to prevent excessive nickel from causing embrittlement |
|
Si |
≤ 2.0% |
Deoxidizer |
|
Mn |
≤ 1.0% |
Deoxidizer, improve processing performance |
|
Mo |
≤ 1.0% |
Optional small additions to provide enhanced solid solution strengthening and pitting corrosion resistance |
Physical Properties
|
Property |
Value/Range |
Test Conditions |
|
Density |
8.69 - 8.87 g/cm³ |
Room temperature (20°C) |
|
Melting Point |
1260 - 1390°C |
- |
|
Coefficient of Thermal Expansion (20-100°C) |
11.5 - 12.5 × 10⁻⁶ /K |
- |
|
Elastic modulus (Young's modulus) |
205 - 230 GPa |
Room temperature |
|
Thermal Conductivity (20°C) |
14.5 - 14.8 W/(m·K) |
- |
|
Resistivity |
0.85 - 0.94 μΩ·m |
- |
|
Magnetism |
Non-magnetic (weakly magnetic) |
Cobalt-based alloys are typically non-magnetic or weakly magnetic at room temperature |
Mechanical Properties (Cast/Welded Condition, Typical Values)
|
Property |
Typical Value |
Specification |
|
Hardness (Cast/Weld Overlay Condition) |
45 - 55 HRC(450 - 600 HV) |
AWS A5.21 ECoCr-B |
|
Tensile Strength |
650 - 850 MPa |
- |
|
Yield Strength (0.2% Offset) |
550 - 700 MPa |
- |
|
Elongation |
1 - 3% (brittle material) |
- |
|
Compressive strength at room temperature |
2000 - 2400 MPa |
- |
|
Impact toughness |
Charpy V-notch 5 - 15 J |
- |
Note: Stellite 8 is a brittle wear-resistant material. Its main performance indicators are hardness and wear resistance. It has low tensile strength and extremely poor plasticity, and is generally not recommended for structural components subjected to high tensile loads.
High-temperature performance
High-Temperature Hardness (Core Advantage): Stellite 8 exhibits excellent ability to maintain hardness at high temperatures. Below are typical reference values for hardness variation with temperature:
|
Temperature |
Typical hardness |
|
Room Temperature |
45 - 55 HRC |
|
400°C(750°F) |
42 HRC |
|
600°C(1110°F) |
38 HRC |
|
760°C(1400°F) |
30 HRC |
|
870°C(1600°F) |
22 HRC |
Antioxidant Performance:
In high-temperature oxidation environments, Stellite 8 forms a dense Cr₂O₃ oxide film on its surface. After exposure to air at 800°C for 1000 hours, the oxidation weight gain is less than 1 mg/cm², demonstrating better antioxidant properties than most iron-based heat-resistant steels.
Long-Term Thermal Stability:
When in service at temperatures above 600°C, the alloy exhibits excellent microstructural stability with no significant phase transformation or softening. The allotropic transformation of the cobalt matrix and solid-solution strengthening from tungsten collectively ensure its long service life under high-temperature conditions.
Applicable Media:
1. Seawater, saltwater (excellent pitting corrosion resistance)
2. Oxidizing acids: Nitric acid (superior corrosion resistance at room temperature)
3. Non-oxidizing acids: Sulfuric acid (concentration ≤50%), hydrochloric acid (concentration ≤30%) (corrosion rate typically <0.1 mm/a)
4. Alkaline solutions: Sodium hydroxide, potassium hydroxide (resistant to all concentrations)
5. Organic acids: Acetic acid, formic acid, etc.
6. High-temperature oxidizing atmospheres, sulfur/chlorine-containing gases (forms a protective Cr₂O₃ film on the surface)
Note: Stellite 8 has limited corrosion resistance in strongly reducing acids (e.g., concentrated hot hydrochloric acid) and fluorine-containing media. For high-stress friction conditions, it is recommended to use in conjunction with lubricating media.
Stellite 8 is suitable for high-wear, medium-impact, and high-temperature applications and is recommended for the following fields:
Application Fields
-
Valves and Sealing Industry: High and medium pressure valve sealing surfaces (seats, discs, stems), pump casings, rotating seals, mechanical seals. It offers better wear resistance than Stellite 6 and is suitable for media containing solid particles.
-
Aerospace and Energy: Gas turbine guide vanes, engine valve sealing surfaces, turbocharger seal rings, high-temperature bearings.
-
Oil and Gas: Downhole tool wear parts, drill pipe joints, valve internals, mud pump components, resisting high-speed erosion from sand-laden media.
-
Industrial Machinery and Tools: Hot extrusion dies, hot shear blades, die-casting molds (gates, plungers), extruder screws, cutting edges for plastic processing.
-
Chemical and Petrochemical: Reactor agitator blades, wear-resistant linings on heat exchanger tube plates, pump and valve sealing surfaces, withstanding the combined effects of corrosion and wear.
-
Nuclear Power Industry: Valve seals in nuclear islands, nuclear-grade wear-resistant liners, utilizing its high radiation tolerance and microstructural stability.
-
Shipbuilding and Offshore Engineering: Wear-resistant surfaces of propeller shafts, pump and valve components, resisting seawater corrosion and mechanical wear.
-
Automotive and Internal Combustion Engines: High-performance exhaust valves, rocker arms, turbocharger seal rings, maintaining anti-wear and anti-seizing properties at high temperatures.
-
Steel and Heat Treatment: Hot shear blades, hot saw blades, furnace bottom rolls, guide rolls, withstanding high-temperature oxidation and abrasive wear.
-
Glass and Ceramic Forming: Glass molds, hot extrusion dies, due to their excellent corrosion resistance to molten glass and ceramics.
Delivery and Customization
We offer flexible and reliable supply chain solutions to ensure you receive Stellite 8 materials that perfectly match your project requirements.
|
Form |
 Sheet/Plate
|
 Bar/Rod
|
 Seamless Pipe
|
 Strip/Sheet Coil
|
 Wire/Wire Rod
|
|---|---|---|---|---|---|
|
Conventional Range |
Thickness: 0.5 - 100 mm |
Diameter Φ6-500mm |
Outer diameter Φ10-300mm |
Thickness: 0.1 – 3.0 mm |
Diameter Φ0.5-10mm |
|
Customization Capability |
Special thick/thin rolling, ultra-wide plates; special surface treatment, fixed-length cutting |
Large-sized forged bars (up to Φ800 mm), special-shaped bars, and various heat treatment conditions |
Large-diameter thick-walled pipes, special alloy composition; Pipe end processing (beveling, fixed length) |
Different hardness conditions, special heat treatments (stabilization treatment, grain size control), acid-washed surfaces, electrolytic polishing, coatings, or special protective films |
Special surface treatment, precision drawing |
Why Choose Us? - Reliable Engineering Technology. Dependable Delivery.
We are not just a supplier, but a trusted materials partner for you in China.
Vertically Integrated Production
Own 20,000㎡ facility with 10+ automated lines (8,000+ tons/year). In-house tooling & die center enables rapid customization and effective cost control - no middleman markup.
Strict Quality Control at Every Stage
Full traceability across key QC checkpoints throughout production. 100% compliant with ASTM/ASME, EN, and GB standards. Material test reports available with every shipment.
Reliable Delivery & Export Packaging
10+ years exporting to Europe, North America, Southeast Asia & Middle East with waterproof and anti-rust protection, combined with flexible shipping options ensures safe and on-time arrival.
Sample Validation Before Mass Production
We provide free samples for quality verification, allowing you to place bulk orders only after approval. We ensure consistency from sample to mass production by accurate dimensional measurement and transparent manufacturing.
FAQ
Q: What are the main advantages of Stellite 8?
Q: What heat treatment does Stellite 8 require?
Q: What is the maximum service temperature?
Q: What is the difference between Stellite 8 and Stellite 6?
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