Development of Advanced Forging Alloys
As an advanced manufacturing industry, forging can benefit from the development of advanced alloys used in its products and in the dies it uses to forge them. QuesTek Innovations’ computationally designed materials offer this enhanced performance and have been vetted through the development of best practices at multiple forging houses. Its most notable commercial successes are in its ultrahigh-performance line of Ferrium® steel alloys.
The design of materials that are stronger, tougher, more corrosion-resistant and more durable is often a costly and time-intensive process. Integrated Computational Materials Engineering (ICME) technologies are proven, cost-effective innovation tools that reconfigure the materials-development process and accelerate the design and deployment of novel high-performance alloys in demanding applications. In recent years, the benefits of an ICME approach have been widely recognized and encouraged, most notably through the U.S. Materials Genome Initiative (MGI), which aims to cut the 10- to 20-year material creation-and-deployment cycle by half at reduced cost.
QuesTek Innovations LLC, an internationally recognized leader in ICME, has repeatedly achieved and surpassed this MGI goal. The company was established in 1997 to commercialize Northwestern University Professor Greg Olson’s pioneering work in computational materials design. Through the application of its Materials by Design® methodology – which combines ICME technologies with in-house, captive, proprietary materials-property databases; mechanistic models; and software tools – QuesTek computationally designs, develops and brings to market novel high-performance alloys. These tend to displace incumbent materials that are limited in their performance.
Our most notable commercial successes are in ultrahigh-performance steels, which have been widely used by the forging industry to manufacture components for demanding applications. Licensed to and produced by Carpenter Technology Corp. (Reading, Pa.), QuesTek’s line of Ferrium® steels was designed for ultrahigh performance through improvements in strength, toughness, stress-corrosion-cracking resistance, thermal stability, wear resistance, fatigue resistance and other critical properties. Ferrium steels have been able to introduce cost savings, component life extensions, weight savings, novel part designs and system efficiencies in the aerospace, oil and gas, and automotive industries.
The Ferrium steels are martensitic and utilize efficient strengthening precipitate dispersions to achieve varying combinations of high strength and toughness designed with specific target properties and performance. Ferrium M54® steel is an upgrade in strength and toughness over common forging steels such as 4340, 300M and Maraging 250, with the added benefit of high resistance to stress-corrosion cracking. Ferrium S53® steel is an upgrade to 4340 and 300M by providing a unique combination of ultrahigh strength and improved corrosion resistance. The carburizable gear steels, Ferrium C64® and C61™, provide higher strength, surface hardenability, fatigue resistance and temperature resistance over traditional gear steels such as 8620, 9310, EN36 and alloy X53.
Considering Grain Growth
In the design of the Ferrium steels, consideration was taken to address grain growth during the various thermal processes. Specifically, grain-pinning carbide particles were incorporated into the microstructural design to remain stable at high temperatures and mitigate grain growth, which became an important factor in developing best practices for Ferrium forging. The stability of grain size allowed the opportunity to use higher hot-fire temperatures. This results in reduced flow stress during forging and offers the flexibility of using various forging practices, including open- and closed-die forging.
QuesTek has worked closely with multiple forging houses (such as Scot Forge, SIFCO Forge Group and Larson Forgings) to develop best practices for the manufacture of components from Ferrium steels. Scot Forge, for example, is a forging partner that has had success in forging Ferrium products. They note that in forging the C-5 Galaxy main landing gear, “The S53 material forges beautifully, and the final product exceeded all design criteria.”
Along with the forging vendors, QuesTek worked closely with the entire component manufacturing supply chain (including alloy producers, heat-treatment providers, and machining and finishing vendors) in the development, qualification and manufacture of Ferrium alloys.
Naval Hook Shank Landing-Gear Application
One leading application of Ferrium M54 steel is a safety-critical hook shank landing-gear component on the U.S. Navy’s T-45 platform. Due to its unique combination of high strength, high toughness and stress-corrosion-cracking resistance, M54 steel has more than doubled the life of the previous landing gear, resulting in an estimated savings of $3 million to the Navy.
Although the M54 steel raw-material cost is higher than that of the incumbent steel, the final component provides more than twice the performance versus the incumbent steel for only 1.2 times the overall price, taking into consideration the manufacturing, heat treating and machining costs. With the success of this program, M54 steel is also approved to replace the incumbent steel on F/A-18 for landing-gear components.
The success of M54 steel was highlighted as an MGI success story in a case study sponsored by the National Institute of Standards and Technology (NIST). Interested readers can visit mgi.nist.gov for additional information. The performance enhancements of this steel have brought improvements to industries beyond aerospace through adoption as input shafts for high-performance racing, case running tools for oil and gas, fasteners for military applications and more.
Air Force Landing-Gear Components and More
Ferrium S53 steel has allowed the U.S. Air Force to fly components without the need for cadmium plating (used for corrosion protection) while improving corrosion resistance versus the incumbent 300M and 4340 steels. A variety of demonstration landing-gear components have been forged and manufactured from S53 steel, which are flying on Air Force platforms including the T-38, A-10, C-5 and KC-135. S53 steel has seen further adoption as aerospace bolts and fasteners as well as in multiple components on SpaceX’s Falcon 9 rocket. It is being used for the main landing-gear piston on the Dragon spacecraft.
High-Performance Gear Steels
Ferrium C64 steel was designed and developed based on the need for a next-generation high-performance gear steel. With high surface hardenability up to 64 HRC, enhanced temperature resistance and improved fatigue properties, C64 steel allows for the lightweighting of components, increased power through drivetrains and improved oil-out durability for transmission gearboxes.
Bell Helicopter and Sikorsky/Lockheed Martin are evaluating and qualifying C64 for next-generation helicopter transmission gears under the Army Future Advanced Rotorcraft Drive System (FARDS) program. Ferrium C61 steel is being considered for applications in which lower surface hardness but higher core strength and fracture toughness are beneficial. The leading example is the application of C61 steel to the forward and aft rotor shafts of the Block II upgrade for Boeing’s Chinook CH-47 platform, where qualification is under way.
A Look at Forging Dies
In addition to designing novel high-performance alloys for the forging industry, QuesTek’s expertise in computational modeling can provide solutions to address limitations and enhance the durability of forging dies. Thermomechanical fatigue and abrasive wear lead to forging-die failures in certain forging processes. New forging-die alloys or hard-face coatings specifically designed to address these issues can improve die life. These approaches would lead to more effective forging practices with reduced cost and material waste, along with the ability to forge high-performance materials that have higher flow stresses.
Benefits of Advanced Materials
With increasing demand by industry for improved-performance components, the forging industry could benefit from advanced materials. QuesTek’s computationally designed materials offer this enhanced performance and have been vetted through the development of best practices at multiple forging houses.
QuesTek is accelerating the advancement and adoption of advanced materials in multiple industries and platforms. Building on the benefits already realized through existing collaborations, the company is seeking further partnerships with forging houses that would be interested in offering improved materials solutions to their customers.
Lead author Kerem Taskin is a Materials Applications Engineer with QuesTek. He can be contacted at firstname.lastname@example.org or 847-425-8210. Co-author Jeff Grabowski is Manager of Product Commercialization for Questek. He can be reached at email@example.com or 847-425-8241. Co-author Chris Kern is a Materials Deployment Engineer for QuesTek. He can be reached at firstname.lastname@example.org, 847-425-8242.