Haynes® 188 (UNS R30188) Cobalt Alloy
Core Advantage: ZYTC Alloy supplies Haynes® 188 (UNS R30188) cobalt-nickel-chromium-tungsten alloy in bar, sheet, plate, and custom forms. Unlike commodity suppliers, we verify every batch's chemistry and mechanical properties in our in-house laboratory, ensuring your combustor liners, transition ducts, and afterburner components perform reliably at temperatures up to 1095∼C (2000∼F).
Why Specify Cobalt Alloy 188?
When gas turbine combustor temperatures exceed the limits of nickel-based alloys, engineers need a material that maintains strength without sacrificing oxidation resistance. Haynes® 188 is a solid-solution-strengthened cobalt alloy that delivers a rare combination: excellent high-temperature strength, outstanding resistance to sulfate deposit hot corrosion, and good post-aging ductility.
The key differentiator is its lanthanum addition (0.02每0.12%). This trace element modifies the protective oxide scale, making it exceptionally tenacious and retarding diffusion even during prolonged exposure at 1095∼C. In burner rig tests simulating gas turbine environments, Alloy 188 showed significantly lower metal loss than Alloy 625 and Alloy X under sulfate deposit hot corrosion conditions.
Composition & Heat Treatment: What Determines Performance
| Element | Nominal Range (wt%) |
|---|---|
| Cobalt (Co) | Balance |
| Nickel (Ni) | 20.0 每 24.0 |
| Chromium (Cr) | 20.0 每 24.0 |
| Tungsten (W) | 13.0 每 16.0 |
| Lanthanum (La) | 0.02 每 0.12 |
| Carbon (C) | 0.05 每 0.15 |
Heat Treatment: Solution anneal at 1163每1191∼C (2125每2175∼F) followed by rapid cooling or water quench. Unlike age-hardenable alloys, 188 is not strengthened by precipitation aging; its properties come from solid-solution strengthening and carbide precipitation during service exposure.
ZYTC Quality Note: The lanthanum content is often overlooked, but it is the single most important trace element for oxidation resistance. We use Direct Reading Spectrometers to verify La within the narrow 0.02每0.12% window for every heat, ensuring your components form the protective oxide scale as designed.
Mechanical Properties: Room Temperature to 1093∼C
Typical tensile properties for solution-annealed sheet:
| Temperature | 0.2% Yield Strength | Ultimate Tensile Strength | Elongation |
|---|---|---|---|
| RT | 483 MPa (70 ksi) | 982 MPa (142 ksi) | ~51% |
| 649∼C (1200∼F) | 309 MPa (45 ksi) | 821 MPa (119 ksi) | ~59% |
| 871∼C (1600∼F) | 261 MPa (38 ksi) | 324 MPa (47 ksi) | ~104% |
| 1093∼C (2000∼F) | 59 MPa (8.5 ksi) | 85 MPa (12 ksi) | ~50% |
At 1093∼C, Alloy 188 retains meaningful strength while maintaining ductility〞a balance that many competing alloys cannot achieve. For spring applications, cold-worked 188 can reach tensile strengths up to 250 ksi (1725 MPa).
Welding & Fabrication: Avoiding the Common Pitfalls
Alloy 188 is readily weldable by GTAW (TIG), GMAW (MIG), electron beam, and resistance welding. However, two rules are non-negotiable:
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Interpass temperature must stay below 93∼C (200∼F). The alloy＊s low thermal conductivity and high thermal expansion mean excessive heat input promotes cracking.
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Post-weld heat treatment is generally not required. The alloy maintains its properties in the as-welded condition when proper interpass control is maintained.
Matching composition filler metal is recommended. For section thicknesses greater than 9.5 mm, Haynes® 230-W® filler may be considered.
Engineering Tip: If you are welding 188 combustor components and experiencing heat-affected zone cracking, the first thing to check is your interpass temperature. We can provide welding parameter guidance based on our experience supplying this alloy to aerospace fabricators.
Quality Verification at ZYTC
Cobalt alloys for gas turbine service cannot be supplied on trust alone. Our in-house laboratory verifies:
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Direct Reading Spectrometer: Full chemistry including La and trace elements, ensuring compliance with AMS 5608 / UNS R30188.
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Universal Testing Machine: Tensile properties at room temperature and elevated temperatures, verifying yield and elongation meet your design allowables.
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Metallurgical Microscope: Grain size and carbide distribution, which influence creep life and thermal fatigue resistance.
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| Direct Reading Spectrometer | Universal Testing Machine | Metallurgical Microscope |
Applications
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Aerospace Gas Turbines: Combustor cans, transition ducts, afterburner liners, flame holders.
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Land-Based Gas Turbines: Combustor components requiring hot corrosion resistance.
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Chemical Processing: Components exposed to molten chloride salts and sulfidizing environments.
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Nuclear: High-temperature structural components where cobalt alloy properties are required.
Available Forms & Specifications
| Form | Specification | Size Range |
|---|---|---|
| Sheet / Plate | AMS 5608 | Custom cut to size |
| Bar / Rod | AMS 5608 / UNS R30188 | Diameter per request |
| Welding Wire | AMS 5801 | Spools or cut lengths |
Standards: UNS R30188, AMS 5608, Werkstoff Nr. 2.4683.
Request a Quote
Send us your operating conditions (temperature, atmosphere, forming requirements) and our technical team will confirm material suitability and provide a quotation with full certification.
Please include:
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Product form and dimensions.
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Quantity.
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Required certification (EN 10204 3.1, AMS 5608 compliance).
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Any special testing (elevated temperature tensile, corrosion testing).
📧 Email: dominic@zytc-steel.com
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