Alloy 188

Alloy 188 – Properties, Applications and Technical Data

Alloy 188, also known as HAYNES® 188, is a cobalt-based superalloy developed for extreme temperatures, aggressive gas environments and high mechanical loads. The alloy offers a unique combination of high temperature strength, excellent oxidation resistance up to approximately 1093 °C and resistance to sulfate scale corrosion. Alloy 188 retains its toughness even after prolonged exposure to high temperatures, and the material has very good weldability and machinability for a superalloy.

Properties of Alloy 188

The balanced cobalt-based chemistry, together with additions of chromium, nickel, tungsten and lanthanum, makes Alloy 188 particularly resistant to thermal shock, creep and oxidative environments. The alloy exhibits excellent structural stability during long-term service and maintains both strength and ductility even near its upper temperature limit.

- Type: Cobalt-based superalloy
- Structure: FCC-based austenitic structure
- Designations: Alloy 188, HAYNES® 188, UNS R30188, Werkstoffnr. 2.4683

Advantages

Exceptional oxidation and corrosion resistance up to approx. 1093 °C
Very good high temperature strength and excellent creep resistance
Resistant to thermal shock and rapid temperature fluctuations
Resistant to sulfate scale corrosion
Good weldability and relatively good formability for a superalloy

Limitations

Higher density than nickel and titanium-based materials
More demanding machining compared to standard alloys
High price due to cobalt and tungsten content
Limited use in reducing environments at extreme temperatures

Typical applications

Aerospace & Turbine Technology

Combustion chambers, burners, liners and afterburner components in gas turbines.

Energy generation

High-temperature components in turbines, heat shields and systems with hot gas flows.

Process industry

Components in oxidative and corrosive gas environments with prolonged temperature stress.

Equipment for extreme environments

Components exposed to hot, corrosive and sulfate-laden atmospheres.

Corrosion resistance

Alloy 188 is extremely resistant to oxidation, especially at temperatures above 1000 °C. The lanthanum content enhances the formation of a stable oxide film, providing long-lasting protection. The alloy also has very good resistance to sulfate plating corrosion, which is often found in gas turbines and combustion environments.

Environments where Alloy 188 performs well:

High temperatures in oxidizing atmospheres
Hot gas flows in combustion systems
Sulfate-laden environments
Thermal cycling and rapid temperature changes

Environments to avoid:

Highly reducing environments at high temperatures
Highly carburizing environments
Certain metal vapor environments at extreme heat

Technical data

UNS Number:	R30188
Werkstoffnummer:	2.4683
Density:	~9.13 g/cm³
Melting interval:	~1300–1355 °C

Chemical composition (%)

Co	Balance
Cr	20.0–24.0
You	20.0–24.0
13.0–16.0
La	0.02–0.12
C	0.05–0.15
Mn	≤ 1.25
Si	0.20–0.50
Fe	≤ 3.0
P	≤ 0.020
S	≤ 0.015
B	≤ 0.015

Alloy 188 combines high temperature stability, good formability, weldability and very strong oxidation resistance, making it optimal for critical components in the energy, aerospace and process industries.

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