AMS 5608: The Definitive Guide to Alloy 188 (UNS R30188) Sheet and Plate
In the relentless pursuit of higher performance in aerospace and industrial power generation, materials are pushed to their thermodynamic limits. For engineers designing components for environments exceeding 2000°F (1095°C), material selection becomes a survival test. Enter AMS 5608, the specification governing Alloy 188 (UNS R30188) —a cobalt-based superalloy that stands as a benchmark for extreme-temperature oxidation resistance and structural stability.
This article provides a detailed technical analysis of Alloy 188 in the sheet, strip, and plate form, covering its chemical complexity, mechanical backbone, market pricing, and the role of specialized suppliers like ZYTC Alloy.
1. The Cobalt Advantage: Chemistry & Specifications
Unlike iron-based or nickel-based superalloys, Alloy 188 uses Cobalt as its base element. This unique matrix provides superior hot corrosion resistance and phase stability under long-term thermal exposure. The alloy is solution-strengthened by Tungsten (W) and refined by Lanthanum (La), a rare earth element that drastically improves oxide scale adhesion.
Nominal Chemical Composition (per AMS 5608)
According to technical data sheets from manufacturers and distributors, the tight chemical tolerances are as follows :
| Element | Weight % | Role in Alloy |
|---|---|---|
| Cobalt (Co) | Balance | Base metal; provides hot corrosion resistance. |
| Chromium (Cr) | 20.0 – 24.0 | Forms protective oxide layer. |
| Nickel (Ni) | 20.0 – 24.0 | Stabilizes austenitic structure. |
| Tungsten (W) | 13.0 – 16.0 | Solid-solution strengthener. |
| Iron (Fe) | 3.0 max | Residual impurity. |
| Lanthanum (La) | 0.03 – 0.15 | Improves oxide adhesion (spallation resistance). |
| Carbon (C) | 0.05 – 0.15 | Carbide former for creep strength. |
| Silicon (Si) | 0.20 – 0.50 | Enhances oxidation resistance. |
Available Forms: While this article focuses on AMS 5608 (Sheet, Strip, Plate), Alloy 188 is also available under AMS 5772 (Bar & Forgings) and AMS 5801 (Welding Wire) .
2. Mechanical Properties & Performance
Alloy 188 is not age-hardenable; its strength comes from a combination of the cobalt matrix, tungsten solute atoms, and carbide precipitates. It retains tremendous ductility even after prolonged exposure to elevated temperatures—a critical factor for components undergoing thermal cycling.
Typical Tensile Properties (Annealed Condition)
Per AMS 5608 standards, Alloy 188 sheet in the annealed condition exhibits a balanced profile of strength and formability .
| Property | Imperial | Metric |
|---|---|---|
| Tensile Strength | 130 – 160 ksi | 900 – 1100 MPa |
| Yield Strength (0.2% offset) | 55 – 75 ksi | 379 – 517 MPa |
| Elongation | 45+ % | 45+ % |
| Density | 0.325 lb/in³ | 9.0 g/cm³ |
Physical Constants:
High-Temperature Endurance:
The defining characteristic of Alloy 188 is its extraordinary oxidation resistance. Due to its high chromium and lanthanum content, the alloy can withstand continuous cyclic oxidation up to 2000°F (1095°C) and intermittent service up to 2100°F (1150°C) . It significantly outperforms Nickel-based alloys like Inconel 625 in sulfur-laden (sulfidation) environments.
3. Fabrication and Heat Treatment
While Alloy 188 is renowned for its strength, it is surprisingly amenable to fabrication, provided the fabricator accounts for its rapid work-hardening rate.
Forming: In the annealed state, the alloy is ductile and can be cold formed. However, due to a high work-hardening coefficient, complex deep draws or bends may require intermediate anneals (Solution treatment at 2150°F / 1175°C followed by rapid cooling) to restore ductility .
Welding: Alloy 188 exhibits excellent weldability. It can be joined via Gas Tungsten Arc Welding (GTAW/TIG) or Electron Beam Welding. The filler metal should be matching Alloy 188 (AMS 5801) to maintain mechanical properties in the heat-affected zone (HAZ).
Hot Working: Recommended forging temperatures range from 2150°F to 2100°F (1175°C to 1150°C) .
4. Market Pricing and Supply Chain (Q2 2026)
The price of Alloy 188 is volatile and driven by cobalt and tungsten commodity markets, as well as the complexity of the mill rolling process.
As of mid-2026, spot prices for AMS 5608 Sheet vary significantly based on volume, origin, and certification paperwork (e.g., ASTM/AMS vs. purely commercial).
Distributor Price (USA/Europe): Typically ranges from 120 per kg for sheet and strip in small quantities.
Factory Direct (Offshore): Sources list factory direct sales for UNS R30188 plate at approximately $800/kg for high-spec material , though bulk sheet orders often trade lower.
Brokerage Markets: Prices vary widely; listings show ranges from ₹999 to ₹8,000 per kg (~96 USD) depending on scrap content vs. virgin certified material .
5. Supplier Spotlight: ZYTC Alloy
For global buyers seeking a balance between strict AMS certification and competitive lead times, ZYTC Alloy has emerged as a significant supplier of Hayne 188 and Udimet 188 products .
Stock and Capabilities:
Unlike many trading houses that only re-sell scrap or remnants, ZYTC maintains a robust production chain. Regarding AMS 5608, they have demonstrable experience in handling complex export logistics, including recent shipments to demanding markets like Japan and India .
Why ZYTC for AMS 5608?
Product Range: They offer the full spectrum of AMS 5608 (Sheet/Strip) and can transition to AMS 5772 (Bar) or AMS 5801 (Wire) for complete project sourcing .
Inventory: ZYTC maintains ready-to-ship inventory of Alloy 188 sheet ranging from 0.5mm to 3.0mm thickness, with production capabilities extending to 300mm thick plate for heavy machining .
Certification: They specialize in supplying materials that pass rigorous final inspection, ensuring compliance with international standards required for aerospace and turbine construction .
Contact Information:
For specific pricing on cut-to-size sheets or large-tonnage plate, buyers can contact ZYTC Alloy directly:
📧 Email: daisy@zytcsteel.com
📲 WhatsApp: +86 17335753350
🌐 Website: https://www.zytcalloys.com/en/products.html
AMS 5608 (Alloy 188 / UNS R30188) remains the "gold standard" for cobalt-based sheet applications. While the initial material cost is higher than that of stainless steel or standard nickel alloys, its resistance to sulfidation and cyclic oxidation at extreme temperatures ensures a longer lifespan for combustor liners, transition ducts, and afterburner components.
When procuring this material, buyers should prioritize suppliers like ZYTC Alloy who provide transparent chemical certifications and can handle the logistical complexity of high-performance alloy shipping. Whether you require a small strip for a prototype flame-holder or heavy plate for an industrial gas turbine shroud, Alloy 188 delivers where other alloys melt away.
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