Up-Armoring Large-Scale Structures at the Point of Need Using Low Cost High-Pressure Cold Spray

Cold spray processing is a solid-state, additive manufacturing method of developing coatings with fine microstructures, high tensile strength and adhesion, superior wear performance, and tailorable anodic or cathodic corrosion protection. Combat, tactical and amphibious structures use armor plate to provide protection against ballistic and fragmentation threats. For example, steel and aluminum armor plates are used on Army light tactical and fighting vehicles, where the composition, microstructure and processing are carefully designed to yield the optimal combination of protection, weight and mechanical properties. Higher hardness and thickness is required to defeat the increasing severity of the threats, which can be obtained by modifying the composition and processing of the armor plate. These higher hardness, thick armor plates are heavy and prone to cracking. When used as structural components, residual stresses induced during fabrication, environmental effects, and dynamic loading under typical operating parameters can result in crack initiation, propagation and ultimate failure, leading to decreased fleet and mission readiness. One potential solution for this issue is the use of a multi-layered structure, where a nanostructured, high hardness coating can be applied to a less crack susceptible structural steel, resulting in a structure that offers high penetration resistance and low crack susceptibility. Additionally, this coating can be used to retrofit and repair existing armor panels to provide additional ballistic resistance. Presented will be the mechanics and microstructure, as well as ballistic performance of newly developed ballistic resistance coatings on A36 structural steel. All work is performed on a mobile high-pressure cold spray unit to enable point-of-need repair, sprayed in atmospheric conditions, while utilizing nitrogen as the processing gas.