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1160 |
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Wednesday, June 04, 2008, Room 05 4:00 PM Polymers, Environmental-Friendly Coatings, Non Destructive Testing Testing coatings directly on coated parts without destroying any additionally coated samples, polymer-based coatings and environmental-friendly coatings |
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The effect of surface chemistry and morphology on the properties of HVAF PEEK single splats |
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Benjamin Withy / Defence Technology Agency, New Zealand Margaret Hyland/ University of Auckland, New Zealand Bryony James*/ University of Auckland, New Zealand |
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Thermal spray of polymers has had limited investigation due to the narrow processing windows that are inherent to polymer powders, especially their low temperatures of thermal degradation. The polymer poly aryl ether ether ketone (PEEK) has a high thermal degradation temperature and high resistance to alkaline and acidic attack. These properties led to PEEK being selected for investigation. To minimise thermal degradation of the particles, the high velocity air fuel (HVAF) technique was used. To investigate the effect of substrate pre-treatment on single splat properties, single splats were collected on aluminium 5052 substrates with six different pretreatments at two different substrate temperatures. The surface chemistry and morphology resulting from each pre-treatment was determined by x-ray photo-electron spectroscopy (XPS) and atomic force microscopy (AFM) respectively. The single splats collected were then imaged by scanning electron microscopy (SEM) and image analysis was performed with ImageJ, an open source scientific graphics package. It was found that on room temperature substrates (23ºC), the properties of PEEK single splats were predominantly unaffected by substrate surface pre-treatment. On substrates held at 323ºC however it was found that substrate pre-treatment had a significant effect on the circularity and area of single splats, and also on the number of splats deposited on the substrates. Increases in splat circularity, area, and the number of splats deposited on the surface were linked to the decrease in aluminium hydroxide on the substrate surface and the decrease of surface roughness. This proved that surface chemistry and roughness are crucial to forming single splats with good properties, which will lead to coatings of good properties. |