Laser Engineered Net Shaping (LENS) Phase II
DoD Participants: U.S. Navy Naval Undersea Warfare Center Keyport; U.S. Air Force Warner Robins Air Logistics Center; U.S. Army Anniston Army Depot
Component corrosion, fatigue, material degradation, wear, and obsolescence are conditions which impact weapon system readiness for warfighters and peacekeepers. Many of the Department of Defense (DoD) ships (300), aircraft and helicopters (15,000), strategic missiles (1,000), and ground combat and tactical vehicles (350,000) include high-value components which are challenging and expensive to replace via the DoD materiel supply chain, and difficult or impossible to repair by conventional technologies. Cannibalization is becoming more common as new replacement parts are difficult to locate for aging weapon systems.
To extend the life of aging aircraft, combat vehicles, artillery and small arms for DoD, there is a need for more sophisticated component repair and overhaul techniques. This includes improving existing methods, as well as developing novel processes to enhance repair capabilities. Components such as turbine blades, vanes, impellers, stator assemblies, and rotating air seals are just a few types of the high-cost components requiring repair to extend weapon system life. Corrosion, fatigue, wear, stress and damage require component repair or replacement during overhaul processes.
As tanks, ships, submarines, and aircraft continue to operate beyond their intended life, part obsolescence management becomes an increasing challenge for asset sustainment, compromising military readiness. Vendor attrition, supply base degradation, long lead times for forged and cast parts, lack of available technical data packages, and logistics management are becoming more common, significantly increasing the cost of sustainment. If an overhaul line is stopped because a component is unavailable, the cost of the component itself becomes irrelevant compared to the cost of the delay.
The performance and reliability of components and assemblies are critical to ensure that weapon systems are combat ready. For some parts, a hard facing layer may provide an adequate solution for wear and/or corrosion resistance. However, many other critical components, made from difficult to process materials, require more complicated repair processes. These repairs can involve three-dimensional (3D) features, radial- oriented structures and directionally-solidified or single-crystal materials.
Many of todays repair procedures give inconsistent results and do not lend themselves to automated operations. Manual processes such as welding can add several variables into the repair process that could affect the quality and the cost of the finished product. Operator fatigue, skill, experience, humidity and other environmental factors present variables which have a direct effect on repair reliability and repeatability.
Due to exacting metallurgical requirements for many gas turbine engine components, traditional repair technologies have compromised part integrity, deeming some components non-repairable. Traditional repair techniques have failed for many reasons, including:
· Excessive heat input causing part distortion
· Uncontrolled atmosphere and process environments skill base
· Unacceptable material properties (i.e. porosity) controls
· Inconsistent manual processes
· Dwindling welding artisan
· Lack of in-situ process.
In summary, there is a need for improved repair techniques to provide cost avoidance for both DoD and commercial enterprises. Such techniques can also provide benefit in lead-time reduction, quality improvement and repeatability.
Under the National Center for Manufacturing Sciences (NCMS) Commercial Technologies for Maintenance Activities (CTMA) program, a collaborative project was formed to validate the merits and feasibility of a material deposition repair technology called LENS, as well as meet or exceed the anticipated annual cost avoidance provided by Anniston Army Depot (ANAD).
The LENS Phase I project was successful in transitioning the LENS technology to ANAD, who have since developed and qualified repairs for several components previously deemed difficult to repair or non-repairable. The repair of these parts was estimated to result in avoiding $6M in costs the first year of its use. Subsequent years have resulted in even more cost avoidance as additional parts have been identified for this repair process. ANAD personnel indicated of even greater benefit was the increased throughput and thus increased readiness provided to repair previously unrepairable parts. ANAD purchased a second LENS machine to handle the increased demand for LENS machine time. Further details are available in an NCMS LENS Phase I Final Report, dated December 11, 2002.
As a result of the success of LENS Phase I, the project partners were honored to receive the prestigious NACFAM Small team Defense Manufacturing Excellence Award at the Defense Manufacturing Conference, December 2005 in Dallas, TX. This award is a tribute to LENS potential to significantly impact materiel readiness and cost avoidance.
Although the LENS Phase I project accomplished its goal, there were many enhancements required to transition LENS R&D technology into an industrial hardened system. The extensive testing and usage of the LENS 850 machine delivered to ANAD revealed multiple design improvements and system upgrades required to field the LENS technology broadly across DoD. Also, Command level approval and original equipment manufacturer repair certification are required before LENS can realize its potential to deliver higher quality repairs at a reduced cost to DoD.
A model 850R was designed suitable for repair applications and the production environment and volumes encountered at Maintenance depots.
The application efforts produced mixed results. Optomec, the technology provider company, repaired component parts from collaborative partners Rolls-Royce, Boeing Rocketdyne, and Siemens Westinghouse. The partners then provided engineering analysis of the repaired parts. The consensus was that the LENS process was technically successful in repairing the selected alloys in terms of physical properties, lack of porosity, near net-shape profiles, soundness of repair, and repeatability. Cost avoidance, because of this new process was mixed. (Actual cost avoidance was considered proprietary by some industrial participants. Several non-weldable alloys were not readily adaptable to this process and require further study. Efforts on aluminum component parts at WR-ALC were not successful and require additional study. Several partners felt that the process showed great promise for their applications, but that the process needed additional maturation with regard to greater automation to achieve cost benefits.
A completed LENS 850R system was fabricated and installed at the NUWC Keyport, Washington. Technology transfer and the proper training was provided to Keyport personnel.
NUWC Keyport identified numerous high-cost DoD torpedo and submarine components that are good candidates for the LENS repair process. The process would extend the lifecycle of torpedo cylinder barrels considerably over the existing repair process. Torpedo cylinder barrels are subject to severe pitting and corrosion in critical cylinder liner sealing surfaces within the combustion chamber. Corrosion is likely caused by the corrosive mixture of combustion by-products and salt water. The previous repair process consisted of machining the sealing area until the pits were removed. To make up for the removal of material in this sealing area, an extended liner was placed into the cylinder bore. However, only a limited number of repairs could be made on each bore before an insufficient amount of material remained. When the machining exceeded a predetermined limit on one or more cylinder bores, the entire asset was scrapped. Replacement costs for the cylinder barrel range from approximately $8K to $22K, depending on quantities being procured. The LENS repair process will be utilized to build up the cylinder barrel bore surfaces to the original drawing requirements eliminating the need to scrap assets. An economic analysis of the repair using the LENS laser deposition process shows a cost avoidance of $90K per year over the purchase of new assets.
Torpedo aft fuel tanks are another application in which LENS will be used to repair corroded surfaces. There are currently 41 fuel tanks identified for LENS repair. The economic analysis of the repair using the laser deposition process shows a cost avoidance of $500K in the next year avoiding the purchase of new assets.
Submarine connector rods, part of the operating mechanisms for submarine stern and sail planes, are another application in which LENS will be utilized. The current repair process is conventional welding and has a resulting 80% fall-out of components (which are scrapped). The fall-out is due to insufficient material hardness in the repair area from the resulting large heat affected zone (HAZ) inherent to conventional welding. In comparison to welding, LENS has one-third the total amount of heat input to the substrate resulting in a much smaller HAZ. The small HAZ provides much greater material properties and sufficient hardness within the repair area. The LENS repair process will be utilized to build up the connector rod surfaces to the original drawing requirements eliminating the need to scrap these assets. An economic analysis of the repair using the LENS process shows an avoidance of $110K per year to the purchase of new assets.
Submarine high-pressure air compressor crankshafts are currently scrapped at a rate of approximately six per year due to the same repair issues as the connector rods. Using the LENS process to repair these assets shows an estimated avoidance of $150K per year over the purchase of new assets.
There is a definite need to incorporate new repair technologies into Navy ship and submarine repair. This is especially significant in the current environment when weapons systems and vessels are placed under even more demanding deployment schedules. New repair technologies, such as LENS, have a great potential to perform higher-quality repairs with reduced repair lead times resulting in a significant savings to DoD.
An important mission of NUWC Keyport is to provide solutions for solving obsolescence issues and implementing new repair technologies for a wide variety of Navy and non-Navy customers. The new capabilities provided by the CTMA LENS Phase II system will support NUWC Keyports mission by providing important new capabilities for both repair of high-value components as well as near net shaping for new manufacturing applications. While the majority of this workload involves applications in Navy weapons systems and support equipment and ship/submarine/aircraft platforms, NUWC Keyport also has significant non-Navy workload in this area with customers. NUWC Keyport will be pursuing certification and utilization of the unique LENS capabilities on a variety of non-Navy components including Air Force jet engine components, Coast Guard vessel castings, Army heavy-vehicle components and a wide variety of multi-service components from the Defense Logistics Agency (DLA). NUWC Keyport is working with non-Navy customers from Fort Lewis Army Station, U.S. Coast Guard (Seattle), McChord Air Force Base, Tinker Air Force Base, Defense Supply Center Columbus and others on potential non-Navy applications for LENS.