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| Abstract No.: |
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Scheduled at:
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Thursday, June 08, 2017, Hall 28 2:00 PM
Equipment / Consumables & Powders, Wires, Suspensions II
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| Title: |
Suspension plasma spray YSZ feedstocks and delivery system for improved spray distance and cost effective throughput
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| Authors: |
Brian Callen* / Oerlikon Metco (Canada) Inc., Canada
Riston Roccio-Heller / Oerlikon Metco (US) Inc., USA
Jing Liu/ Oerlikon Metco (US) Inc., USA
Omar Sabouni/ Oerlikon Metco (US) Inc, USA
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| Abstract: |
Yttria-Stabilized Zirconia (YSZ) suspensions are currently popular in developing strain resistant columnar structured thermal barrier coatings by Suspension Plasma Spray (SPS) as a less costly alternative to conventional EB-PVD . Coatings produced by SPS have a disadvantage of reduced usable spray distance, compared to conventional APS, due to quenching of the plasma by the suspension liquids, which are most commonly alcohol-based. The reduced spray distance can interfere with the coating process for substrates with complex geometries such as turbine blades. This paper shows how spray distance can be increased by using a larger suspension particle size that is not normally considered for SPS. Such large particle suspensions are shown capable of producing columnar or segmented YSZ coating microstructures that are similar to those produced by submicron particle suspensions, but at longer and more practical spray distances. Another limitation to SPS process technology is the delivery system of feedstock from the point of manufacture to the SPS feed hopper. Current commercial suspensions are produced, shipped and stored in small ready-to-use containers. Such ready-to-use suspensions, particularly those with flammable liquids such as alcohol, have safety issues and high costs related to specialized packaging, transportation of dangerous goods, storage, handling and shelf life. As a result, there is a desire to provide suspension feedstocks by alternative delivery systems that are more efficient and cost effective, particularly for anticipated commercial scale SPS operations. An alternative suspension delivery system is discussed involving dry loosely agglomerated feedstock that is pretreated with dispersant, packaged, transported and stored in the same manner as conventional thermal spray powders. The pre-formulated feedstock is then constituted into fresh suspension by the end-user with locally sourced liquid solvent and appropriate high-speed mixing equipment. This alternative delivery system for suspensions provides lower cost materials and process flexibility that is particularly suited to commercial scale SPS coating facilities.
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