National Center for Manufacturing Science (NCMS) Advances Cold Spray
Cold spray is a solid-state coating deposition method in which powdered metals are accelerated through a nozzle to velocities sufficient to cause plastic deformation and bonding. In this way, layers of new metal can be added to worn surfaces, which can refurbish components subject to corrosion, wear, or impact damage and build up dimensions lost to other degradation processes. Cold spray is a particularly useful method for repairing components that don’t respond well to processes that produce high heat.
Shortly after the discovery of cold spray, in the mid-1980s, then called “kinetic spray,” the National Center for Manufacturing Sciences (NCMS) assisted in bringing this technology to United States. In 1994, NCMS invited one of the principal researchers of cold spray, Dr. Anatolii Papyrin, to make a presentation explaining the cold spray process to a multi-company thermal spray coating group. [1] That same year, NCMS began supporting Dr. Papyrin to conduct a cold spray demonstration project at the University of Toledo, where he launched the first cold spray system in the US, researched cold spray, and published several early technical reports. NCMS also established a second US cold spray research system at the General Motors Technology Center in Warren, MI. [2] Over the years, NCMS has held a variety of technology forums on cold spray, in coordination with the Joint Technology Exchange Group (JTEG). More recently, NCMS has facilitated three Commercial Technologies for Maintenance Activities (CTMA) projects to advance cold spray technology.
Cold Spray for Sustaining Maritime Assets
When NAVSEA, NAVAIR, and the US Marine Corps sought innovative cold spray solutions for the maintenance and sustainment of maritime assets, NCMS organized a Commercial Technologies for Maintenance Activities (CTMA) collaboration to fulfill this objective. The project, titled “Advancing Additive Repair Technologies and Cold Spray for Sustainment of Maritime Assets,” began in 2019 and is scheduled for completion in August 2022. [3] This joint effort brings together top research universities and industrial partners to expand the scope of potential repairs available to ships while underway to avoid dry docks or piers unless completely necessary. By building an ecosystem of training, support, and inspection capabilities, the project team aims to maximize cold spray applications across a wide range of maritime assets.
Cold spray has the capability to add new metal onto worn surfaces so critical features can be re-machined back to tolerance, allowing parts previously destined for scrap to be reused. This project focuses on developing high-volume capability to produce unique metallic cold spray powders with optimized microstructure for cold spray deposition. In the first phase, the team demonstrated cold spray technologies in three Naval shipyards, testing a variety of equipment including multiple spray devices, robots, spray booths, and atmospheric control equipment. [4] In the second phase, they expanded the demonstration to an additional shipyard and added portable and thru-hatch cold spray technology that can be used to provide in-situ repairs. The final phase will create assisted and virtual reality-based training tools to help crew members adapt and keep pace with the accelerated rate of change in advanced AM practices.
This initiative will reduce both the time and cost of delivering mission critical maintenance and sustainment for Naval vessels. Once parts are qualified and certified to be repaired using cold spray on-board, inventory levels could be lowered, providing more space for other critical equipment. Using on-board technologies will enable technicians to eliminate some instances of repair that previously would have required shore facilities, thereby increasing mission availability.
The project’s cold spray solutions will have an immediate application in the commercial maritime industry. Implementing the ability to make repairs while at sea will give vessels the opportunity to continue towards port with critical cargo and to accomplish their missions in lieu of being delayed in a facility waiting for repairs. Overall, this project is expected to reduce maintenance and sustainment costs, improve availability, and extend the life of maritime assets.
Cold Spray for Repairing Aerospace and Ground Vehicle Parts
To assist the US Armed Forces with expanding the capabilities of cold spray to repair more parts for the aerospace and ground vehicle industries, NCMS launched a CTMA collaboration, “Improved Hardware Sustainment through Solid State Additive Manufacturing Development.” This effort, which began in 2019, brought together the armed forces, industry, and academic partners to advance the use of cold spray processes. The initiative will focus specifically on using cold spray for repair and modification of aerospace and ground vehicle systems in both commercial and DOD applications.
The overall objective is incorporate a broader set of metal powders into the cold spray process to allow the repair method to be used on a wider range of materials, and to develop the hardware needed to apply those materials. Specifically, the project will develop new processes that are suitable for non-structural and structural repair of a broad range of aluminum, steel, nickel, and titanium-based alloys. Furthermore, by broadening the capabilities of cold spray, this project will enable improvements in the quality and performance of components to be repaired, thereby extending the lifetime of vehicles, and other high-value assets, and reducing maintenance and sustainment costs.
The team will develop a mobile cold spray system that can be transported to and utilized for maintenance in a military depot. Unlike conventional cold spray stationary systems, which require a dedicated facility in which to perform the repair, this new unit provides a fully capable cold spray repair system mounted on a platform that can be brought to different locations within the facility to perform repair activities. Another new development in the mobile cold spray unit is the ability for the robotic delivery system to use collaborative path planning as an approach to pre-programming. The operator can safely “teach” the robot where it needs to go by physically positioning it at the correct place and angle at various points along its journey and record those points. The robot can then follow the pre-programmed path, which allows the operator to avoid hand-entering program parameters into the robot pendant. The development of path planning and optimization for complicated geometries will allow cold spray repair to be available for a wider range of parts needing refurbishment.
The results of this initiative will be to greatly enhance DOD maintenance capabilities for aerospace and ground vehicles. More specifically, the project will facilitate more rapid, reliable, and consistent production of repair parts; reduced overall equipment downtime and maintenance costs; shortened supply chain lead time with increased requisition fulfillment; reduction in on-hand inventory requirements; and expanded warfighter readiness. Along with these benefits to the DOD, this collaboration will develop materials and systems that can be leveraged by private industry to assist with repairs to aerospace and ground vehicles. The project is scheduled to wrap up in 2023.
Cold Spray for Reducing Lifecycle Maintenance Costs
Recent advances in commercial cold spray technologies and processes have been very effective at protecting parts from corrosion and repairing damaged parts. However, it is challenging to apply these coatings to parts of intricate or complex geometry such as gun barrels or engine cylinders. The intent of this initiative, “Exploration of Cold Spray Technologies to Reduce Lifecycle Maintenance Costs,” which began in 2020, is to develop the advanced manufacturing process and capability to apply a high-temperature, wear-resistant cold spray coating to the inner diameter of a large caliber cannon tube and machine that coating to blueprint geometry and specification. Combining current advanced manufacturing methods, such as cold spray and waterjet technologies, along with new materials, this initiative will assess possible replacements for chrome-plated refractory barrel liners.
The benefit of this project is that cold spray allows for hard-to-remove components in a system to be repaired, rather than removed and replaced, without concerns for their long-term structural integrity or strength. Lessons learned can be applied as a maintenance solution by both military and commercial organizations tasked with maintaining complex metal parts in numerous applications. For the DOD, finding an effective and efficient process to repair damaged parts instead of replacing them will have significant impact on maintenance, sustainment, and readiness across all the services. This project, which is slated to end in February 2023, is expected to provide wear-resistant coatings, eliminate corrosion, reduce maintenance and sustainment costs, improve warfighter readiness and lethality, extend asset lifecycle, and decrease environmental impact and waste.
Notes
[1] Smith, M.F. “Introduction to Cold Spray,” in High Pressure Cold Spray: Principles and Applications, edited by Charles M. Kay and J. Karthikeyan. ASM International, 2016. Pg. 8.
Singh, Harminder, et al. “Development of cold spray from innovation to emerging future coating technology.” The Brazilian Society of Mechanical Sciences and Engineering. 35 (2013): 233.
[2] Smith, M.F. “Introduction to Cold Spray,” in High Pressure Cold Spray: Principles and Applications, edited by Charles M. Kay and J. Karthikeyan. ASM International, 2016. Pg. 8.
[3] Callihan, Phil. “Cold Spray for Maritime Repair.” CTMA Magazine. Issue 8. September 24, 2020. pp. 60-1. https://www.flipsnack.com/ncms1/copy-of-2020-ctma-magazine-issue-eight.html.
[4] Callihan, Phil. “Cold Spray Advances Vision of the Shipyard of the Future.” CTMA Magazine. Issue 9. May 12, 2021. pp. 54-5. https://www.flipsnack.com/ncms1/2021-ctma-magazine-issue-nine-tp52ppz2gx.html