The objective of this SERDP Exploratory Development (SEED) Statement of Need (SON) is to rigorously benchmark the environmental footprint of cold spray or other solid-state manufacturing methods to include energy usage, toxic chemical usage, critical element usage, and waste generation for corrosion repair applications against traditional methods, particularly plating lines. Additionally, theoretical and experimental efforts should develop methods to improve cold spray or other solid-state manufacturing sustainability for a given application or set of applications. Given the many applications of cold spray and solid-state manufacturing, proposals should focus on a single application only.   

Proposals should include a plan to conduct a preliminary Life Cycle Analysis¹ (LCA) to help indicate the life cycle cost benefit associated with the cold spray or solid-state manufacturing process relative to the incumbent process. Proposals should establish a life cycle framework that can compare to the baseline and mature as the technology or process advances through the development and acquisition processes. This tiered approach aims to develop and document a minimum data set at each stage of research and development that can be used to make informed decisions and streamline transition to an acquisition program. The LCA may include varying depths of data and information that can inform: the goal and scope of an analysis; the identity and quantity of relevant inputs and outputs to the system; and the estimation of life cycle impacts and costs. A preliminary LCA would help indicate the cost benefit associated with the proposed process relative to current processes. 

Successful completion of this research effort will result in life cycle benefits to help transition cold spray and solid-state manufacturing into Department of War applications. In particular, details of performance and cost benefits and tradeoffs associated with cold spray or other solid-state repair will help identify repairs that are most appropriate for transition and would benefit from further investment to validate the technology for the application. 

Cold spray is a form of metal additive manufacturing that uses high pressure gases to accelerate metal powders to ballistic speeds at a substrate. The metal is heated, but at temperatures well below its melting point.  The combination of heat and speed cause the powders to consolidate extremely well when they strike a solid substrate producing highly dense materials.  Past work successes have shown value in replacing plating, filling in holes and wear marks due to corrosion and wear, as well as formation of structural materials to manufacture or repair structural parts on equipment, ground vehicles, and air systems.  Cold spray is used in various aerospace applications and some naval and automotive applications.   

Most high-performance applications for cold spray have used helium as the carrier gas because this gas can accelerate powder faster than any gas except for hydrogen, while being safer than hydrogen.  Helium is a critical gas and its cost has increased dramatically lately.  There are methods to recover and recycle the helium, but these are inefficient, with recovery rates of less than 50%. Nitrogen has been shown to be effective for many applications.  Low pressure cold spray has even shown benefit in certain commercial applications.   

Electroplating involves the use of aqueous metal ions and electric potential to control the deposition of the metal onto a substrate.  The deposition rate is very slow relative to cold spray. Despite it being aqueous, volatilization is possible causing exposure to metal ions, which is problematic for various plating operations, such as chrome plating where hexavalent chromium ions are typically used.  Electroplating of alloys is complicated because of the tendency for the different ions to plate under different potentials.  This results in relatively limited alloy selection typically resulting in compromising material performance needed.  Alloying in cold spray is possible through prepared alloy powders and through mixture of powders during the cold spray process. 

Various other solid-state manufacturing exits including but not limited to thermal spray, friction stir welding, general welding, and friction stir additive manufacturing.  There are performance and cost benefits and tradeoffs of each of these methods relative to plating and cold spray. 

SEED Proposals: Proposers with innovative approaches to the SON that entail high technical risk or have minimal supporting data may submit a SEED Proposal for funding up to $350,000 and approximately one year in duration. Such proposals may be eligible for follow-on funding if they result in a successful initial project. The objective of these proposals should be to acquire the data necessary to demonstrate proof-of-concept or reduction of risk that will lead to development of a future Standard Proposal. Proposers should submit SEED Proposals in accordance with the SEED Proposal instructions and deadlines.  In summary, SEED proposals forgo the preproposal and submit a proposal with a technical page limit of 10-pages.  

John La Scala, Ph.D.  

SERDP & ESTCP Program Manager 

Weapons Systems and Platforms  

Email: john.j.lascala.civ@army.mil