Udimet® / Waspaloy® – superalloys for extreme loads
Characteristics of Udimet® and Waspaloy® alloys
Udimet® and Waspaloy® belong to a group of high-temperature superalloys designed for use in conditions where classic heat-resistant and creep-resistant steels fail to provide sufficient durability. These materials are primarily used in aviation, power generation, gas turbines, the space industry, and other devices simultaneously exposed to high temperatures, mechanical loads, creep, oxidation, and high-temperature corrosion.
The Udimet family includes various materials with distinct chemical compositions and strengthening mechanisms. Therefore, all Udimet and Waspaloy alloys should not be considered a single group of nickel alloys with identical properties.
Waspaloy – UNS N07001 is a precipitation-strengthened nickel superalloy in which the γ′ phase plays a very important role. Udimet 188 – UNS R30188 and Udimet L-605 – UNS R30605 are high-temperature cobalt-based alloys. Their mechanism for achieving high strength and thermal stability is different from that of classic nickel precipitation-hardening superalloys.
Waspaloy® – a precipitation-strengthened nickel superalloy
Waspaloy – UNS N07001, W.No. 2.4654 is a nickel-chromium-cobalt superalloy with additions of molybdenum, titanium, and aluminum. It was developed to perform under high mechanical loads at elevated temperatures.
Its structure is based on an austenitic nickel-based γ matrix. Appropriate heat treatment leads to the formation of fine, coherent phase precipitates. γ′ – Ni3(Al,Ti)This phase is one of the basic strengthening mechanisms of Waspaloy and allows it to maintain high strength even at temperatures at which the properties of conventional structural alloys deteriorate significantly.
Aluminum and titanium additions are primarily responsible for the formation of the γ′ phase, while chromium increases resistance to oxidation and high-temperature corrosion. Cobalt influences matrix stability and high-temperature properties, among other things, and molybdenum provides additional solution strengthening.
Thanks to its carefully selected chemical composition and multi-stage heat treatment, Waspaloy is characterized by high tensile strength, creep resistance and resistance to long-term loads at elevated temperatures.
Waspaloy creep resistance
One of the most important properties of Waspaloy is high creep and creep rupture resistanceCreep is the process of slow and permanent deformation of a material under prolonged load at high temperature.
In gas turbine components, this process is particularly important because the component can operate simultaneously for thousands of hours under the influence of high temperatures and high mechanical stresses.
The stable nickel matrix and γ′ phase precipitates limit dislocation movement and maintain the material's high strength at elevated temperatures. This is why Waspaloy is used in the most critical components of aircraft engines and gas turbines.
Waspaloy's resistance to oxidation
The significant chromium content enables the formation of a protective oxide layer on the surface of Waspaloy, which limits further oxidation of the material.
Oxidation resistance is particularly important in turbine engine components and power equipment, where the material remains in contact with hot gases for long periods.
However, a distinction must be made the maximum temperature at which the alloy exhibits oxidation resistance, from the temperature at which it can safely withstand high mechanical loads for thousands of hoursThe allowable design temperature depends on the stress, required durability, heat treatment, and the specific product form.
Waspaloy heat treatment
The properties of Waspaloy are strongly dependent on the heat treatment used. Typical processes include solution heat treatment and subsequent aging steps to control the size, distribution, and proportion of γ′ phase precipitates.
Changing heat treatment parameters allows for a change in the trade-off between strength, ductility, creep resistance, and fatigue life. Therefore, Waspaloy's mechanical properties should not be reported as a single value independent of the material's condition.
Welding and machining Waspaloy
Waspaloy is a material that is significantly more demanding technologically than typical stainless steels and many standard nickel alloys. Its high content of γ′-phase-forming elements requires careful attention to the material's condition, heat input, and subsequent heat treatment during welding.
The alloy may be susceptible to cracking during welding and heat treatment processes. In components subject to high loads, welded joints require particularly careful design. The high-temperature properties of welds may be inferior to those of the properly heat-treated base material.
Machining is also demanding due to the high strength of the material, the tendency to harden during machining and the high loads on the tools.
Udimet® 188 – a high-temperature cobalt-based alloy
Udimet 188 – UNS R30188 is a cobalt-nickel-chromium-tungsten alloy designed for operation at very high temperatures. Unlike Waspaloy, it is not a classic nickel superalloy strengthened with γ′ precipitations.
The alloy contains approximately 20–24% chromium, 20–24% nickel and a significant amount of tungsten, while the material's base is cobalt. A small addition of lanthanum supports the formation of a durable and protective oxide layer.
Udimet 188 combines high strength at elevated temperatures with very good resistance to oxidation, high-temperature corrosion and good metallurgical stability during long-term thermal exposure.
The material retains good ductility after prolonged exposure to high temperatures and is characterized by good formability and welding properties.
Udimet 188 resistance to oxidation and high-temperature corrosion
One of the most important features of Udimet 188 is its ability to operate at very high temperatures. The alloy exhibits very good oxidation resistance during long-term exposure at temperatures reaching approximately 1095°C.
The high chromium content combined with the addition of lanthanum promotes the formation of a compact and well-adhered protective layer. Udimet 188 also demonstrates good sulfurization resistance and high resistance to some forms of high-temperature corrosion associated with sulfate deposits.
It should be emphasized that the temperature around 1095°C primarily refers to oxidation resistance. This does not imply the ability to withstand maximum mechanical loads at this temperature. Permissible structural stresses decrease with increasing temperature.
Application of Udimet 188 in gas turbines
The combination of oxidation resistance, high temperature strength, metallurgical stability and good weldability makes Udimet 188 particularly suitable for hot section components of gas turbines.
Typical applications include:
- gas turbine combustion chambers,
- combustion chamber linings,
- flame stabilizers,
- transition channels and elements of hot gas flow systems,
- aircraft engine afterburner components,
- covers and components exposed to direct exposure to hot gases.
In these applications, not only mechanical strength is particularly important, but also resistance to heating and cooling cycles and maintaining structural stability during long hours of operation.
Udimet® L-605 – UNS R30605
Udimet L-605 – UNS R30605 is another high-temperature cobalt-based alloy. This material is also known by other trade names, including HAYNES® 25.
The alloy contains significant amounts of chromium, nickel, and tungsten. The high chromium content provides good oxidation resistance, while tungsten provides strong solution hardening and helps maintain mechanical properties at high temperatures.
L-605 is characterized by high strength at elevated temperatures, good oxidation resistance and relatively good wear and seizure resistance.
It is used, among others, in gas turbine components, combustion chambers, aircraft engine components, components operating at high temperatures and specialized applications requiring high mechanical and thermal resistance.
Waspaloy and Udimet 188 and L-605 – basic differences
The most important difference between these materials is the type of matrix and the strengthening mechanism.
Waspaloy is a nickel-based superalloy whose very high mechanical properties are achieved primarily through the controlled precipitation of the γ′ phase. It is particularly useful in components subjected to high mechanical stresses at elevated temperatures.
Udimet 188 is a cobalt-based alloy whose greatest advantages are very high oxidation resistance, thermal stability and maintaining good properties during long-term exposure to high temperatures.
Udimet L-605 It is also a cobalt-based alloy and utilizes primarily solution strengthening. It combines high strength at elevated temperatures with good oxidation and wear resistance.
Therefore, these materials should not be considered simple substitutes. Waspaloy is particularly interesting for highly mechanically stressed turbine components, while alloys 188 and L-605 are very useful in hot-end components where oxidation resistance, high-temperature corrosion, and thermal stability are paramount.
Mechanical properties
There should be no single common range of Rp0,2, Rm, elongation, and hardness for Waspaloy, Udimet 188, and L-605. These are materials with different matrices, chemical compositions, strengthening mechanisms, and heat treatment states.
In the case of Waspaloy Mechanical properties are strongly dependent on saturation and aging. The material can achieve very high yield strength and tensile strength, and its primary advantage is maintaining high strength and creep resistance at elevated temperatures.
In the case of Udimet 188 i L-605 More important than the very high yield strength at room temperature are thermal stability, oxidation resistance, high-temperature strength and retention of properties after long-term thermal exposure.
Accurate values of mechanical properties should always be related to the specific grade, product form, testing temperature and heat treatment condition.
Standards and markings
Waspaloy: UNS N07001, W.Nr. 2.4654. For bars, forging material and other forged products, it is used, among others, ASTM B637There are also a number of AMS specifications for aerospace applications.
Udimet 188: UNS R30188. The material is primarily covered by AMS aerospace specifications, including: AMS 5608 for sheets and strips and AMS 5772 for bars, feedstock and forgings.
Udimet L-605: UNS R30605. The material is listed in numerous industrial and aerospace specifications. Alloy R30605 is also used in medical applications covered by relevant material requirements, including ASTM F90.
The standard should always be selected for the specific product form and application. The UNS designation identifies the alloy's composition, while the requirements for properties, delivery condition, dimensions, and testing are derived from the relevant product standard.
Typical Applications of Waspaloy and Udimet Alloys
Aviation – turbine engine components, turbine discs and rings, shafts, compressor components, combustion chambers, linings, transition channels and other components of the hot engine part.
Energetics – industrial gas turbines, high-temperature installation components, parts of power equipment operating under long-term thermal and mechanical loads.
Space industry – drive system components and components operating in extreme thermal conditions.
Furnace and metallurgical industry – high-temperature device elements, covers, handles and components exposed to oxidation and long-term exposure to high temperatures.
Specialized equipment – components requiring a combination of high strength, creep resistance, structural stability and high-temperature corrosion resistance.
Selection of a high-temperature superalloy
The selection between Waspaloy, Udimet 188, and L-605 should take into account not only the maximum operating temperature. Mechanical stresses, required service life, creep resistance, oxidizing conditions, hot gas composition, temperature cycling, and the potential for high-temperature corrosion are also important factors.
For highly stressed turbine components, the alloy's properties after appropriate heat treatment and the stability of the strengthening phase are crucial. For combustion chamber and hot gas duct components, oxidation resistance, metallurgical stability, thermal fatigue resistance, and the ability to fabricate welded structures may be of greater importance.
For this reason, comparing superalloys solely on the basis of maximum operating temperature may lead to incorrect material selection.
Forms of delivery
Depending on the grade and specification, Waspaloy and Udimet superalloys are available as, among others:
- bars and feedstock for forging,
- forgings,
- rings,
- sheets and strips,
- wires,
- welding materials,
- semi-finished products intended for further processing.
The availability of a specific product form depends on the grade, manufacturing standard, dimensions and required heat treatment condition.
Species available in Alfa-Tech's offer:
- Udimet 188 – nickel and cobalt alloy, heat and corrosion resistance,
- Udimet L-605 – very good resistance to oxidation and creep, also in chemical environments,
- Waspaloy – a classic aircraft superalloy, excellent creep resistance up to 800°C.
Division of nickel alloys
Nickel alloys can be divided into several main families, differing in chemical composition, properties, and typical applications. Below are the most important groups, along with examples of grades available from Alfa-Tech:
Nickel alloys
Inconel® – nickel and chromium superalloys
Alloys with very high resistance to oxidation and creep at high temperatures. Used in the energy, aviation, and chemical industries.
Grades: Inconel 600, Inconel 601, Inconel 625, Inconel 686, Inconel 718, Inconel X-750, Inconel HX.
Incoloy® – nickel, iron and chromium alloys
They combine corrosion resistance with good structural stability. They are particularly valued in the chemical and petrochemical industries.
Species: Incoloy 800 H/HT, Incoloy 825, Incoloy 925, Incoloy DS, Incoloy 330, Incoloy A-286.
Nimonic® – high-temperature superalloys
Precipitation-strengthened materials used in aviation and gas turbines are characterized by high resistance to creep and thermal fatigue.
Types: Nimonic 75, Nimonic 80A, Nimonic 90, Nimonic 263, Nimonic 901.
Udimet® / Waspaloy® – superalloys for extreme loads
Used in aircraft engines and the energy industry, where the highest resistance to creep and thermal fatigue is required.
Species: Udimet 188, Udimet L-605, Waspaloy.
Monel® and pure nickel – chemical and marine resistance
Monel (nickel-copper alloys) and pure nickel are materials resistant to seawater, acids, and alkalis. They are frequently used in the marine, chemical, and specialized equipment industries.
Grades: Monel 400, Monel K-500, Nickel 200, Nickel 201.
Special alloys – Invar®, Kovar®, Permalloy
Materials with unique physical properties—low coefficient of thermal expansion, dimensional stability, or controlled magnetic permeability. Used in electronics, optics, and precision instruments.
Species: Invar 36, Kovar, Permalloy, Nilomag 77.
Hastelloy® / Haynes® – corrosion and high temperature resistant alloys
Alloys with high resistance to aggressive chemical environments, oxidation, and creep. Used in the chemical, energy, and aviation industries.
Grades: Hastelloy B-2, B-3, C-276, C-22, C-4, C-2000, G-30, G-35, X, N; Haynes 214, 230, 242, 282, HR-160.
Inconel®, Incoloy®, Nimonic®, Monel® and Udimet® are registered trademarks of Special Metals Corporation. Waspaloy® is a trademark of ATI Allvac / Precision Castparts, Hastelloy® is a trademark of Haynes International, Invar® and Kovar® are owned by Imphy / ArcelorMittal.