Cobalt-based Alloy 6
CO 6 is a cobalt-based wear-resistant superalloy, which monopolizes the field of extreme working conditions by virtue of “high wear resistance × corrosion resistance × high temperature strength and toughness”. The following is a systematic analysis from six dimensions:
I. Standards and brand system
1. Implementing standards
- Aviation/military industry: AMS 5894 (aviation material specification, covering the properties of forgings and bars) and SAE J467B (automotive engineering standard, defining the technical requirements of wear-resistant parts);
- General processing: refer to ASTM B438 (chemical/mechanical properties of cobalt-based alloy bars), but the core manufacturing standard is AMS/SAE.
2. Brand correspondence
- UNS number: UNS R30006 (American Uniform Numbering System);
II. Chemical composition (mass fraction%, typical range)
CO 6 is designed by “Co matrix+Cr/W/C strengthening phase”, and the synergistic effect of elements is remarkable:
| element | Content range | Core role |
|---|---|---|
| Co | Allowance (~55%) | Stabilize the matrix at high temperature and provide corrosion resistance and toughness. |
| Cr | 28~32 | Cr₂O₃ oxide film is formed, which is resistant to high temperature oxidation and seawater/acid and alkali corrosion. |
| W | 3.5~5.5 | WC/WC hard phase is precipitated to improve the wear resistance (hardness reaches HV1500+). |
| C | 0.9~1.4 | Cr₇C₃ and WC carbides are formed with Cr/W to strengthen the matrix. |
| Fe | ≤3.0 | Auxiliary strengthening, over-limit reduction of corrosion resistance (strict control of impurities) |
| Ni | ≤3.0 | Stabilize austenite and improve low temperature toughness |
| Mn | ≤2.0 | Deoxidation+optimization of casting fluidity |
III. Mechanical properties (typical value, as-cast/annealed)
CO 6 properties crush conventional alloys, focusing on the core advantages of “wear resistance+high temperature”;
| Performance index | typical value | Contrast 316L stainless steel. |
|---|---|---|
| tensile strength | 1000~1300 MPa | 100% higher （316L≈600 MPa） |
| yield strength | 800~900 MPa | 150% higher （316L≈310 MPa） |
| extensibility（δ₅） | 5~10% | 75% lower（316L≈40%） |
| hardness | 38~45 HRC | 85% higher （316L≈20 HRC） |
| heat resistance | Long-term tolerance to 800℃ | 100% higher （316L 长期≤400℃） |
IV. Requirements for Heat Treatment and Processing
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Heat treatment (optimizing structure and releasing property):
- Stress relieving after casting: heat preservation at 800~900℃ for 2~4 hours, and air cooling (eliminating casting stress and stabilizing carbide distribution);
- Repair after welding: anneal at 750~850℃ (repair heat affected zone, prevent cracks and restore corrosion resistance).
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Processing characteristics (high hardness brings challenges):
- Casting: lost wax casting is preferred (precision forming complex parts such as turbine blades and valve seats);
- Machining: cubic boron nitride (CBN) tool+high pressure cooling, low speed cutting (to avoid tool wear, surface roughness Ra ≤ 1.6 μ m);
- Welding: TIG welding (ERCoCr-A welding wire) needs to be preheated to 300℃ (cobalt-based alloy has poor thermal conductivity and thermal stress is easy to crack).
V. Main application fields (“ultimate solution” for extreme working conditions)
With the advantage of “life× performance”, CO 6 monopolizes high-value scenes (the cost is 3 times that of stainless steel and the life is 10 times):
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Aerospace:
- Engine: turbine blade edge (resistant to 800℃ gas erosion, life is twice that of titanium alloy), combustion chamber liner (corrosion resistance+wear resistance);
- Landing gear: wear-resistant bushing and hinge point (high impact+wear resistance, replacing titanium alloy to reduce cost by 30%).
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Energy and chemical industry:
- Valves: oil drilling blowout preventer valve seat (resistant to high pressure mud+corrosion, replacing tungsten carbide to reduce cost by 40%), chemical pump impeller (resistant to acid and alkali+cavitation);
- Nuclear power: control rod guide sleeve (radiation+300℃ high temperature water corrosion resistance, long-term service without aging).
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Machinery and tools:
- Cutting tools: woodworking tools, metal cutting tips (wear life is 3 times that of cemented carbide, suitable for dry cutting/difficult-to-machine materials);
- Wear-resistant parts: mill housing bushing, hammer head of mine crusher (wear-resistant, life 5 times of ultra-high manganese steel).
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Medical field:
- Implants: artificial hip joint ball head (wear-resistant+biocompatible, life is over 20 years, replacing ceramics to reduce cost by 50%), dental implant (body fluid corrosion resistance);
- Surgical instruments: bone saw, orthopedic drill (high hardness+sterilization and corrosion resistance, excellent accuracy retention).
Key summary
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Core advantages:
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Wear-resistant ceiling: carbide hardness HV1500+, abrasive/adhesive wear resistance 10 times higher than stainless steel;
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All-environment corrosion resistance: the corrosion rate in seawater, acid and alkali and high-temperature gas is less than 0.01 mm/year;
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No softening at high temperature: the tensile strength at 800℃ still exceeds 600 MPa(316L 400℃ has been reduced to 300 MPa).
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Limited challenges:
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Cost-sensitive (cobalt price accounts for 70%, and the price fluctuates greatly);
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Complex processing (high hardness requires special technology, and the manufacturing cost increases by 50%).
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C0 6 is a “benchmark of cobalt-based alloy”. Through Cr-W-C ternary strengthening, it has become an “irreplaceable high-end material” in the scene of extreme wear resistance and high temperature corrosion, redefining the life boundary of industrial core components.