2017 | AFC ACCOMPLISHMENTS 91 readiness levels were pursued: namely, electrochemical deposi- tion (ECD), vacuum plasma spray (VPS), and cathodic arc physical vapor deposition (PVD). While the PVD technology required minimal adaptation for any substrate, ECD and VPS coatings needed extensive development for compatibility with the SiC substrate (Figure 1). The initial effort led by Dr. Ang focused on the development of first-generation coatings through the three approaches.The ECD coatings are yet to prove of value due to unacceptable level of cracking after processing.The VPS coatings failed to deposit an intended phase of the coating material on the SiC substrate. Therefore, these two technologies were determined to require signifi- cant more efforts toward demon- strating the technical feasibility. On the other hand, the PVD technology resulted in apparently intact coatings with various materials. Therefore, selected PVD coatings of Cr, CrN, and TiN were further evaluated for mechanical properties, helium permeability, and hydro- thermal corrosion. The mechanical properties evalua- tion was also performed by Dr. Ang (Figure 2). All of the PVD coatings on the SiC/SiC composite substrates exhibited adequate tensile debond strength per American Society for Testing and Materials (ASTM) D4541. However, the scratch testing according to ASTM E2546 indicated the highest delamination resistance for the metallic Cr coating and significant variations in delamina- tion resistance for CrN coatings depending on the condition of deposition.The helium permeability testing performed by Dr. Hu revealed the gas tightness for all of Cr, CrN, and TiN coatings applied to small diameter SiC/SiC tube substrates as measured at room temperature up to slightly more than atmospheric pres- sure. Finally, the autoclave testing for hydrothermal corrosion performed by Dr. Raiman indicated that Cr and CrN are promising compositions for coatings. The future works include additional characterization of as-coated and corroded materials, examination of the coated specimens following neutron irradiation in inert and PWR water loop environments, and the second round of coating optimi- zation based on feedback from the present evaluation.