Case Study: Ferrium® N63™: QuesTek's Answer to One of Aerospace's Biggest Challenges
SituationThe U.S. Navy recognized that certain aircraft would eventually need a materials upgrade to perform better and reduce the number of costly parts replacements and inspections. Its goal was to utilize a surface-hardenable stainless steel for bearing applications. Such a material did not exist at the time, which prompted the Navy, through Small Business Innovation Research (SBIR) funding, to release a solicitation for proposals. In a bit of a twist, as you will read, QuesTek’s development of Ferrium® N63™ in response to the Navy wound up being usable for wider industry applications.
ChallengeExisting bearing components in certain parts of helicopters, jets, and other aircraft belonging to the Navy and next generation aerospace fleets are vulnerable to corrosion caused by moisture during storage or steam during operation. Water deposits and corrosive media that accumulate on the surfaces of the bearings can lead to pitting that can act as initiation sites for early failures. Presently, there is a lack of high performance bearing materials that provide both the necessary properties for these applications and stainless properties on the bearing surface. As a result, other methods to prevent corrosion such as masking, submersion in oil/closing off the bearing to atmospheric exposure, etc. are often required, which add time, cost, and/or weight to the system.
Though it wasn’t a problem at the time, the Navy anticipated it could be down the line and took mitigative and preemptive measures. A new steel had to be created that met the requirements for these bearing applications, but the material needed to possess the adequate combination of mechanical properties and also be stainless.
SolutionThrough Phase I and Phase II SBIR programs, QuesTek met the Navy’s requirement with its development of Ferrium N63 steel. This novel alloy is a nitridable stainless steel for bearing, gear, and other wear-critical applications that demonstrates a unique combination of high-surface hardness, fatigue life, thermal resistance, core strength and ductility, including down to cryogenic temperatures.
Using its ICME approach, QuesTek leveraged its cadre of Ferrium steels, modifying microstructural concepts that yielded Ferrium N63’s unique properties:
- Nitridable for high surface hardenability
- Optimized combination of strength and toughness
- High hardenability for robust thermal processing
- Elevated and extended temperature service
OutcomesFerrium N63 met all of the Navy’s goals and is now in the qualification phase for a multitude of industry applications:
- Fixed wing and helicopter aerospace
- Space exploration
- Industrial bearings
- Off-shore/marine wind turbines
- Marine applications
- Gear applications
QuesTek applied its ICME expertise and methodology, including accelerated insertion of materials, to predict the properties across multiple production lots and expedite the time to qualification. QuesTek is currently pursuing SAE AMS specification.