Bibliography: pages 68-70. / An investigation involving the vibratory cavitation erosion of WC-Co alloys was undertaken in order to determine the mechanisms of material removal. Nineteen grades of WC-Co alloys were studied. These alloys had been previously characterised according to microstructural and mechanical properties. Further characterisation by way of Young's modulus and density of the materials was undertaken. An investigation of the i nfluence of various parameters on cavitation erosion established a binder content dependence on erosion. For two grain sizes, erosion was found to increase to a maximum at 12 vo1-% binder content (1.8 μm grain size) and 23 vol-% binder (2.8 μm grain size). The main mode of material removal was found to be cobalt removal followed by WC grain pull-out. In high binder content alloys, cobalt removal was predominant with little loss of WC grains. X-ray diffraction showed that the allotropic phase transformation of the binder under cavitational attack was beneficial to the erosion resistance of these alloys. The erosion of low binder content alloys was controlled by the contiguity of the WC skeleton. Maximum erosion occurred at binder contents which corresponded to the combination of a fragile WC skeleton and a small volume of available cobalt for strain induced transformation.

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DoD EO/IR applications continue to push imaging technology. Next generation advances require new material systems, novel device structures, as well as the improvement and development of read out integrated circuits. The common methodology used to assess devices and materials is to process test chip structures and focal plane arrays. Test chips have advantages over focal plane arrays; such as, variable area and stand alone devices and can be measured as a function of bias and temperature; however, focal plane arrays are the heart of the imager, but are measured through the read out integrated circuits, which can add complexity to the measurement and to the extraction of properties. Differences between a test chip and a focal plane array make it difficult to relate test chip characterization with focal plane array performance and the interaction of defects and the impact they have to the image. Therefore, it is vital to be able to characterize the detector array directly from 77 to 300 K. This thesis presents the design for a transparent cryogenic probe card based on a silicon carbide substrate. An inspection into the design for the bonding printed circuit board and its compliant structures is included. The design for the silicon carbide probe die is explored. The design and process for fabricating tungsten probe tips is discussed. Results on research efforts are presented showing the validity of the design based upon fabrication outcomes. It is recommended that future work explore additional tungsten tip fabrication methods.

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