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Superalloys to the Rescue
Traveling the friendly skies is back in full swing. In the United States more and more people are taking to the skies to reach their destination – be it for work, family, or for fun. In 2022, the U.S. airlines carried 194 million more passengers than in 2021, up 30% year-to-year. For the full year of 2022, January through December, U.S. airlines carried 853 million passengers (unadjusted) up from 658 million in 2021 and 388 million in 2020 (Statistics). As with every mode of transportation, safety is extremely important. One component of having a safe mode of transportation is its engine. How exactly does it work, what materials make it function, and what makes it safe? One answer to those questions is superalloys.
What is a Superalloy?
Superalloys are “based on nickel, cobalt or iron with large additions of alloying elements to provide strength, toughness, and durability at
high temperatures” (Aerospace Materials: Past, Present, and Future). In simpler terms, a superalloy is the combination of two or more elements of which one element is Ni, Co, or Fe. The added elements offer benefits such as the ability to withstand high heat, corrosion resistant, thermal CREEP defamation resistance, higher mechanical strength, and resistance to oxidation at elevated temperatures.
Superalloys for Gas Turbine Engines
Superalloys have played a central role in the development of jet engine technology. The development of superalloys with better high-temperature and hot-corrosion properties together with advances in engine design and propulsion technology has resulted in great improvements in engine performance (Aerospace Materials: Past, Present, and Future). For example, improvements in the high-temperature properties of superalloys over the last 20 years have helped to increase the thrust of jet engines by more than 60% while fuel consumption has fallen by 15-20%.
Superalloys are used for engine components that operate above 550°C. These areas may include the blades, discs, vanes, and other parts found in the combustion chamber and other high-temperature engine sections. For example, nickel-based superalloys are the preferred material for materials used in the hottest engine components, such as high-pressure turbine blades and discs. These materials must have high strength, fatigue life, fracture toughness, creep resistance, hot-corrosion resistance, and low thermal expansion properties. Nickel-based superalloys have the capability to operate at temperatures up to 950-1200°C. In comparison, aluminum and carbon-fiber based composites are typically utilized within the coolest sections of the engines (cool meaning operating at temperatures below 150°C). These areas can include parts of the fan and inlet casing. Additionally, titanium alloys are used in engine components with operating
temperatures below 550°C which may include parts in the fan and compressor sections (Aerospace Materials: Past, Present, and Future).
As it pertains to corrosion, cobalt-based superalloys are used for jet engine components that require excellent corrosion resistance against hot combustion gases. “These alloys contain 30–60% cobalt and high concentrations of nickel, chromium and tungsten which provide good resistance against lead oxides, sulfur oxides and other corrosive compounds in the combustion gas” (Aerospace Materials: Past, Present, and Future).
EAG as a Strategic Partner for Gas Turbine Engine Testing
Eurofins EAG Laboratories (EAG), a NADCAP certified company, has provided aerospace materials testing services for over 50 years. Using advanced analytical tools and proven methodologies, EAG can support a broad range of aerospace materials testing. One technique utilized is Glow Discharge Mass Spectrometry (GDMS). GDMS is a highly sensitive trace element analysis that can provide data for a wide range of elements from 0.1 wt% to sub ppm levels. Other techniques include EAG’s suite of Inductively Coupled Plasma techniques including Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). ICP-MS is a trace element analysis technique similar to GDMS that can cover a broader range of quantitative analysis with sub ppm sensitivity tests for the major compositions (i.e. nickel is 80% of the alloy). Lastly, Instrumental Gas Analysis (IGA) is used to test for gas forming elements, such as hydrogen, carbon, nitrogen, oxygen and sulfur. The sensitivity of IGA is in the range ppm to weight %.
EAG’s scientists and engineers are experts at translating scientific questions into novel study designs and test systems and have applied advanced analytical methodologies to answer complex engineering and manufacturing questions. Contact us today to learn more about our Aerospace industry expertise.
Works Cited
- “Aerospace Materials: Past, Present, and Future.” Aerospace Materials: Past, Present, and Future. Woodhead Publishing Limited, 2012. 15-38. 1 September 2023.
- Statistics, Bureau of Transportation. Full Year 2022 U.S. Airline Traffic Data. 16 March 2023. 1 September 2023.
Related Resources
- Brochure: Aerospace and Defense Brochure
- Newsroom Article: EAG Secures DLA MIL-STD 883 TM 1018 Suitability
- Newsroom Article: EAG Successfully Completes ISO 17025 Accreditation and Expands Scope to RGA Testing
- Newsroom Article: EAG Metallurgical Experts Investigate Turbine Failure
- Application Note: How Do You Shape Tomorrow's Aviation?
- Service: Services for Aerospace & Defense Industry
- Technique: GDMS
- Technique: ICP-MS
- Technique: ICP-OES
- Technique: LA-ICP-MS
- Technique: IGA
- Industry: Aerospace
- Industry: Defense
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