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首页> 美国政府科技报告 >Erosion Behavior of CVD TiB sub 2 Coatings on TiB sub 2 -Based Ceramic Substrates in High-Velocity Coal-Oil Slurries
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Erosion Behavior of CVD TiB sub 2 Coatings on TiB sub 2 -Based Ceramic Substrates in High-Velocity Coal-Oil Slurries

机译：高速煤油浆中TiB亚2基陶瓷基体上CVD TiB sub 2涂层的冲蚀行为

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The erosion behavior of chemically vapor deposited (CVD) TiB sub 2 coatings deposited on hot pressed TiB sub 2 ceramic substrates was studied by impingement of a liquid stream containing 8 wt % of coal derived solids (SRC-1/sup a/) in anthracene oil upon the CVD surface, and compared with erosion of a high-density uncoated TiB sub 2 ceramic specimen. Erosive exposure of all specimens was conducted at approx. 350 exp 0 C for 1 h at a liquid flow velocity of 100 m/s and an incidence angle of 20 exp 0 between the liquid jet and the specimen surfaces. These conditions simulate those present in pressure let-down valves in direct coal liquefaction processes. The principal materials variables included the microstructure and composition of the TiB sub 2 ceramic substrates, while the CVD coatings were all deposited under identical conditions at 900 exp 0 C from the hydrogen reduction of TiCl sub 4 and BCl sub 3 . The deposited CVD coatings, which were approx. 50 mu m in thickness, exhibited strong preferred orientation as determined by x-ray diffraction. Relative erosion resistance was assessed by determining the maximum depth of the erosion crater formed in the TiB sub 2 surface at the point of jet impingement. For the four CVD coatings exposed, the maximum crater depth values were 0, 1.5, 5.5, and 5.5 mu m, while the uncoated specimen had a depth of approx. 22 mu m. Prior work had shown that only consolidated or single-crystal diamond provided zero crater depths under these conditions. The outstanding erosion resistance of the CVD coatings was apparently related to their crystallographic texture. (ERA citation 07:063260)

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