An investigation into the premature failure of an Alloy 800HT (UNS N08811) oxygen-gas mixer water jacketed end is discussed. Detailed metallurgical analyses showed that gamma prime [Ni3 (Al, Ti)] embrittlement and thermal fatigue cracking led to eventual leakage. The reduced life of the Alloy 800HT (UNS N08811) replacement (problems after only a year) was traced to its higher Al + Ti content (1.1%) compared to Alloy 800H (0.6% Al + Ti) which lasted over two years. While higher aluminum and titanium levels improve high temperature creep and stress rupture properties, both are sigma formers and, at levels > 0.6%, tend to form gamma prime with nickel. The choice of alternative metallurgies requires careful considerations of physical, mechanical and thermal properties as well as an understanding of complex stresses and stress distributions.

Subject
Embrittlement, Water, Materials, Nickel based alloys, Thermal stress, Intergranular cracking, Thermal fatigue, Jackets, Cracking, Aluminum alloys, Brinell hardness, Titanium alloys, High temperature
Keywords:
Alloys 800H, Alloy 800HT, thermal fatigue, gamma prime embrittlement, reformer, burner
© 1994 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).
1994
Association for Materials Protection and Performance (AMPP)
You do not currently have access to this content.