Oxygen Plasma Treatment and Deposition of CNx on a Fluorinated Polymer Matrix Composite for Improved Erosion Resistance (Preprint)

High-performance polymer matrix composites PMCs are an appealing choice for materials in aerospace applications due to their high strength-to-weight ratio and stability over a broad temperature range for thousands of service hours. The use of PMCs in propulsion applications is currently limited only by insufficient resistance to erosion by abrasive media. Erosion-resistant coatings may provide the necessary protection, however their application is not straightforward, as surface preparation is a challenge. Specifically, it is because of the resin-rich outer plies, mold release agents, and fluorinated high-temperature polymer matrices that treatment prior to deposition is required. A low pressure oxygen plasma treatment process was developed to improve adhesion of CNx coatings to a polymer matrix composite. CNx was selected as a protective coating for its high hardness-to-elastic ratio, coupled with elastic resilience. In situ x-ray photoelectron spectroscopy was used to evaluate the effect of the plasma treatment on surface chemistry, and electron microscopy was used to identify changes in the surface morphology of the PMC substrate after plasma exposure. CNx coatings were then deposited on treated PMC substrates. The effect of the plasma predeposition treatment on coating adhesion and erosion resistance was evaluated. The combination of PMC pretreatment and coating with CNx reduced the erosion rate by an order of magnitude.