Nimonic 90 is a nickel-chromium superalloy designed to withstand extreme conditions caused by very high working temperatures. Nimonic 90 is designed to withstand high temperatures with its structure designed with about 20% chromium and additional components of cobalt, titanium and aluminium that work together to form an alloy that does not yield to softening as temperatures increase.
This material ‘s ability to withstand high temperatures without softening as a result of micro-structural changes caused by a controlled heat treatment is a phenomenon metallurgists call the alloy’s creep resistance. Nimonic 90 withstands high temperatures and holds its shape while subjected to consistent developmental changes that would cause high temperature deformation within metals.
Examples of Nimonic 90 Uses
While the Gas Turbine Engine as a whole is this material’s main application, the alloy is primarily used in the Engines Turbine component and associated parts such as guide veins, and other components that operate in very high temperatures (exceeding 800 degree Celsius) and hence in the hot section of the Engines. These are the parts that are often constructed in and are not easily recognizable as constructed in Nimonic 90.
The Performance Trade-offs
There are possible trade-offs with any engineer material, and this material is no exception. The material has a max working temperature around 950 °C. While this is very high, comparing to other single-crystal superalloys is a better benchmark. For these applications, this working temperature is too low.
There are also trade-offs with this material’s machinability. The material’s characteristics which make this material excel are also make is very difficult to machine. These characteristics include high strength and a high resistance to work hardening. Manufacturing operations become more complicated because specialist tools and control of machining processes is needed.
Why It Remains Relevant
The development of more advanced superalloys might give the impression that this material has become outdated. However, there are many reasons to justify it’s presence and contribution to the aerospace industry.
Manufacturing know how is also an asset. The aerospace industry has also formed its working methods around Nimonic 90. The aerospace suppliers can process the metal without problems, their quality control can ensure all specifications, and their maintenance has knowledge of how the components will behave with time. This is valuable institutional knowledge.
Future Directions
Meeting stricter benchmarks for performance and efficiency has fuelled innovations in aircraft engine design for higher operating temperatures. This continuous innovation creates a market for materials that exceed for performance other alloys like this material. Single crystal super alloys and ceramic matrix composites continue to capture market share in modern engines in the highest temperatures zones.
In aerospace engineering, materials that provide a balance between thermal reliability and years of proven engineering losing strength stand the test of time. In many cases, applications do not require engineering materials that push the envelope of innovation. Instead, a reliable engineering material that is well understood will provide a better solution than a cutting edge, state of the art material.
For the engineering who specifies materials and for the professionals who source and buy engines, Nimonic 90 is a well-established technology that balances factors like cost when performing mundane engineering tasks. In aerospace engineering, knowing where a material fits and where it does not is critical to the selection of materials for the application.