Over the last few years, conventional 2,25Cr1Mo grade has been increasingly replaced by 2,25Cr1MoV grade for the fabrication of heavy refining reactors, offering better mechanical properties at high temperatures. This change also improves Hydrogen Induced Disbonding (HID) resistance due to large differences in hydrogen solubility and diffusion behavior between the two grades. The hydrogen trapping ability of 2,25Cr1MoV is also an important parameter to take into consideration.

This paper proposes to explain the differences between the two previously cited grades when facing gaseous hydrogen and then the consequences on HID performance. This demonstration is based both on actual hydrogen diffusion and solubility laws measurements, hydrogen content profile simulations and actual HID tests to validate the conclusions.

Disbonding tests are very often required during fabrication of hydro-treating vessels. This qualification test permits to assess the quality of the stainless steel overlay deposit procedure. As it is difficult to make the link between the testing conditions and the actual service conditions in the reactor wall, studies based on 2,25Cr1Mo grade were performed in the past and transferred into API 934-A1  recommended practice to better fit the test parameters to severity of actual field conditions and then avoid excessive safety.

Subject
Materials, Modeling, Hydrogen content, Degassing, Diffusion, Reactors, Solubility, Interfaces, Steel, Stainless steel, Alloys, Hydrogen, High temperature
Keywords:
Disbonding, Hydrogen Induced Disbonding, Hydro treatment, 2.25Cr-1Mo, 2.25Cr-1Mo-V, Hydrogen Diffusion, Hydrogen Solubility, Trapping Effect
© 2012 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).
2012
Association for Materials Protection and Performance (AMPP)
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