Summaries - Office of Research & Innovation
Back Functionally Graded Cold Sprayed Hybrid Coatings for Multi-Material Structural Repair and Wear Protection
|Division||Graduate School of Engineering & Applied Science|
|Department||Mechanical & Aerospace Engineering|
|Sponsor||Office of Naval Research (Navy)|
As the aviation fleet of the US Navy ages there is an increased need to develop methods and processes for material and component sustainment and repair. Cold dynamic gas spraying (cold spray) has produced exciting possibilities for repairing metallic components with minimal to no machining or heating. Currently, cold spray technology in the Navy has been limited to cosmetic repairs or dimensional restoration. New approaches and advanced materials are need to push the capabilities of cold spray towards structural repair and protection of aerospace structures. The underlying materials properties and performance ultimately are the enablers of new aviation platforms. Many aerospace structures are increasingly being made of lightweight metals (e.g., aluminum, magnesium), and polymer matrix composites. It is hence desirable to focus on the structural repair and protection of those materials.
This proposal seeks to develop a new coating material architecture using cold spray that is integrated into the substrate and functionally graded to provide maximum protection at the surface. A primary objective of this program is to engineer a high adhesion strength gradient onto the coating that prevents delamination failures. Delamination failures of the coating material on the substrate are one of the most common and catastrophic failure modes of layered materials such as coatings. A second major objective is to decrease surface wear rates by an order of magnitude relative to the substrate (component) material, which will be realized by generating an engineered high wear resistant gradient on top of the adhesion gradient. These compositional gradients exhibiting excellent adhesion strength and wear resistance will be generated by harnessing the unique and highly desirable properties of nanoparticle and microparticle reinforcements to generate a functionally graded hybrid coating system. Cold spray is an ideal process to demonstrate this novel coating material architecture because of its additive nature that enables a layer-by-layer deposition of material, enabling a gradient to be introduced by tailoring the composition of each layer. The proposed work will initially focus on developing this new robust coating architecture for Al6061 components (substrate material). Through understanding and careful tailoring of processing parameters the methodology will be extended to protect polymeric materials using the polymer PEEK as an example material. Achieving a multi-material (polymer/metal) repair technique would enable lightweight plastics and polymer matrix composites to be used in applications typically requiring high wear resistance. Conversely, the use of a polymeric material as the core material for a metal based component would lead to drastic weight reduction and enhanced thermal insulation that could have applications beyond structural load bearing.
While cold sprayed deposits are often referred to as coatings, cold spraying can generate several centimeter thick deposits, where the initial substrate could be used only as a sacrificial support if near net shape forming was desirable. The successful generation of a robust approach for depositing cold sprayed coatings that can protect and restore structural materials would enhanced the Navy's manufacturing capabilities at sea and in the field. These new material processes and architectures generated in this program would lead to cold spray technology serving as a tool for expeditionary manufacturing at the point of need. Repair of components in the field would drastically reduce logistical and sustainment costs and reduce the frequency of maintenance intervals. The material system envisioned would enhance performance by enabling the utilization of ultra-lightweight naval and aerospace structures that would normally not be viable for demanding aerospace load bearing applications such as airframes, truss structures, fuselage, aero foil leading edges, and landing strips and pads.