N121-022 TITLE: Development of Advanced Stainless Steel for Aircraft Engine and Lift Fan Gearbox Bearings

TECHNOLOGY AREAS: Air Platform, Materials/Processes

ACQUISITION PROGRAM: JSF-Prop

RESTRICTION ON PERFORMANCE BY FOREIGN CITIZENS (i.e., those holding non-U.S. Passports): This topic is "ITAR Restricted". The information and materials provided pursuant to or resulting from this topic are restricted under the International Traffic in Arms Regulations (ITAR), 22 CFR Parts 120 - 130, which control the export of defense-related material and services, including the export of sensitive technical data. Foreign Citizens may perform work under an award resulting from this topic only if they hold the "Permanent Resident Card", or are designated as "Protected Individuals" as defined by 8 U.S.C. 1324b(a)(3). If a proposal for this topic contains participation by a foreign citizen who is not in one of the above two categories, the proposal will be rejected.

OBJECTIVE: Design and develop an advanced stainless bearing steel for application to aircraft engine and lift-fan gearbox and bearings with a combination of fatigue and corrosion resistance needed to achieve improved component durability.

DESCRIPTION: Ball and roller bearings are integral components of jet turbine engines and the lift-system for fighter engines. To achieve vertical take-off and landing, the lift-fan is continuously injecting moist air that drives corrosion in key transmission components. Typical bearing steels used in industry are inadequate to meet the combination of rolling contact fatigue performance, core fracture toughness, and dimensional stability with good corrosion resistance. New alloy developments by leading steel and bearing manufacturers all lack some degree of bearing performance or corrosion resistance sought by the military. Pyrowear® 675 is an advanced high temperature corrosion resistance case carburized bearing and gear steel that has been shown to offer significant improvements in bearing performance, providing increased benefits to turbine machinery operating in a marine environment [1]. Conventional carburizing techniques have had limited success in meeting all required properties necessary for bearing and gear performance. Typically, these basic mechanical properties and microstructures can be achieved, but corrosion resistance is not substantially better than conventional bearing steels like M50, 52100, or 440C. Recent advances in computational alloy design [2] and new surface processing capabilities like carbo-nitriding [3] and low-pressure carburizing capabilities provide the opportunity to rapidly design advanced, corrosion-resistant bearing steel. Innovations are sought for custom alloy design to optimize material thermal, bearing, corrosion, and core mechanical properties, providing engines and lift-fan components increased corrosion resistance, load bearing capacity, durability, and ease of processing. Working in collaboration with OEM is suggested but not required.

PHASE I: Define key material performance and identify manufacturing requirements for a new alloy in collaboration with government engineers. Generate proof-of-concept designs that demonstrate the feasibility of achieving the desired combination of properties.

PHASE II: Develop alloy and processing techniques. Finalize material specifications and manufacturing. Evaluate performance in bench-scale tests relevant to aircraft engine operating environments.

PHASE III: Manufacture and qualify components fabricated from the newly invented alloy. Develop a commercial supply and aerospace procurement specifications for robust domestic supply of the alloy. Demonstrate corrosion and fatigue reliability improvements leading to cost savings in military platforms.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The new alloy will be applicable to commercial aerospace propulsion systems and other high-performance transmission components requiring improved corrosion resistance.

REFERENCES:
1. Trivedi, H.K., Forster, N.H. & Rosado, L. (2010). Roling Contact Fatigue Evaluation of Advanced Bearing Steels with and Without the Oil Anti-Wear Additive Tricresyl Phosphate. Tribology Letters, 18 December 2010

2. Wright, J.A., Sebastian, J.T., Kern, C.P., & Kooy, R.J. (2010). Design, Development and Application of New High-Performance Gear Steels. Gear Technology.

3. Chin, H.A., Ogden, W.P. & Haluck, D.A. (2007). Carbo-nitrided Case Hardened Martensitic Stainless Steels. U.S. Patent No. 7,156,304 B2, March 6, 2007

4. Grant, D. H., Chin,H. A., Klenke, C., Galbato, A. T., Ragen, M. A., & Spitzer, R. F. (1998). High Temperature Aircraft Turbine Engine Bearing and Lubrication System Development. Bearing Steels: Into the 21st Century, ASTM STP 1327, J. J. Hoo and W. B. Green, eds., American Society for Testing and Materials.

KEYWORDS: Advanced bearing, stainless steel; corrosion resistance; fatigue resistance; alloy; durability; lift-fan gearbox

** TOPIC AUTHOR (TPOC) **

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