In order to improve the durability and cost performance of superheater in high efficiency WTE boiler, new Ni base alloy/YSZ dual coating systems using plasma-jet spray technology has been developed, and then the life of these coatings sprayed on 500°C/9.8MPa high-efficiency WTE boiler superheater was evaluated by the long term field corrosion test.

Three kinds of coating layer of: alloy 625/YSZ, NiCrSiB alloy/YSZ and Cr3C2·NiCr sprayed by 100kW plasma-jet system both on site and on shop were installed in tertialy and secondary superheater having high metal temperature of 450 ~ 500°C, and exposed for more than 1.3 years.

As the results of the field corrosion test, alloy 625/YSZ and NiCrSiB alloy/YSZ coatings with inorganic sealant showed excellent durability more than 1.5 years compaired with conventional NiCrSiB alloy HVOF system in tertialy superheater. Based on the detail investigation of cut-off tube samples, A durability of each coatings reduce with increase in corrosivity of combustion gas. YSZ and inorganic sealant were clarified to work as a penetration barrier for corrosive components in deposits to coating/base metal interface. Especially, in soot blower affected position, Cr3C2·NiCr layer sprayed in secondary superheater peeled off by thermal cyclic factor after four months exposure, while large corrosion prevention effect was observed in Ni base alloy/YSZ layer regardless of partial peeling-off of YSZ layer. An application of Ni base alloy/YSZ coatings for actual boiler is expected in the future.

Subject
Nickel coatings, Corrosion prevention, Coatings, Materials, Tubes, Spray coating, Plasma, Metals, Sealants, Boilers, Steam, Alloys, Durability
Keywords:
waste-to-energy plant, high-temperature corrosion, refuse incineration, corrosion-resistant coatings, plasma-jet spray coating, superheater tube materials, chlorine corrosion, corrosion life evaluation, field corrosion test
© 2004 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2004
Association for Materials Protection and Performance (AMPP)
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