This paper considers material performance in contact with molten vanadium-rich deposits after exposure at 900 C (1650 F) in flowing oxygen for periods typically of 100 hours. Small test coupons were contacted with a 80-20% mixture of vanadium pentoxide and sodium sulfate as corrodant. Silicon coatings were applied to Ni 20Cr, Ni 50Cr, NIMONIC 115 (Ni 15Co 15Cr 5Al 3.9Ti 3.5Mo) and IN 939 (Ni 19Co 22.5Cr 3.7Ti 2W 1.9Al 1.4Ta 1Nb). The major tests were done with Ni 20Cr. Performance was compared with uncoated alloys.

Coatings were applied by pack, vapor deposition, plasma spraying and ion plating techniques. All gave improved performance despite certain limitations. The susceptibility to vanadic corrosion was reduced by as much as 80% with the coated material. Ion-plated coatings were more reliable with respect to good adhesion, uniformity of composition and even thickness. The silicon appears to act in two ways: it sustains or allows the development and retention of a beneficial chromium-rich under-layer and it affects certain physicochemical parameters such as viscosity, wetting and fluidity, etc.

Subject
Nickel coatings, Coatings, Ions, Materials performance, Nickel based alloys, Chromium, Vanadium, Metal oxides, Corrosion attacks, Silicon, Oxygen, Nickel, Oxidation
© 1987 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).
1987
Association for Materials Protection and Performance (AMPP)
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