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| Abstract No.: |
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Scheduled at:
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Tuesday, September 27, 2011, Saal C2.2 11:25 AM
Powders, Wires & Suspensions
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| Title: |
Novel titania feed-stock powder for significant improvements in process economics and enhanced coating properties
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| Authors: |
Atin Sharma* / Sulzer Metco (US) Inc., USA
Montia Nestler / Sulzer Metco (US) Inc., USA
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| Abstract: |
Plasma-sprayed coatings based on titanium sub-oxide powders possess electrical, mechanical and tribological properties making them useful for a number of applications including rotatable magnetron sputter targets. Traditionally used Fused and Crushed (F&C) titania (titanium oxide/sub-oxide) feed stock powders owing to their angular shapes have relatively poor flowability and are limited in achievable high feed rates before deposition efficiencies start to decline. In addition, the coatings made with F&C powders are generally dense and hence, posses high stiffness and limited fracture toughness. This bears the risk of cracking/delamination particularly for thick coatings. To address these issues a new titania feed stock powder has been developed and compared in side-by-side spray tests to standard F&C titania powder of comparable particle size. The spray behavior, achievable feed rates and deposition efficiencies as well as the resulting coating characteristics (microstructure, phase composition) and properties such as electrical resistivity, fracture toughness and wear resistance were evaluated. The new powder not only overcomes the reported feeding problems associated with the F&C powders but also yields 50-100% improvement in deposition efficiency (DE) while producing coatings with improved microstructures. Furthermore, for a given set of process parameters, the DEs obtained with this new powder show little sensitivity to the powder feed rates allowing spraying at much higher feed-rate. This feature of the powder has significant commercial advantages when combined with high throughput guns such as Triplex Pro 200 which yielded an average DE of 66% at feed rate of 300 g/min. Another advantage of the new powder is that it allows for building thick coatings without cracking/delamination. Fundamental principles behind these improvements were explored by studying particle states during spraying using diagnostic tools.
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