“The present project has been supported by Chas S Lewis Co. Inc. to try to develop a cast alloy that has acceptable mechanical properties and excellent resistance to corrosion by sulfuric acid over the entire concentration range (especially for the concentrations between 60 and 80 wt%) at their boiling temperatures. Also, the alloy should have good machinability and weldability, and be economically viable.
It is known that Ni3Si-based alloys have good corrosion resistance in concentrated sulfuric acids, but they are very brittle. In the present study, Ni3Si-based alloys with Ti, Nb, Cu, Cr and Mo additions have been cast and studied with SEM, DTA, AES, and optical microscopy. Their mechanical properties and corrosion resistance in boiling sulfuric acids with different heat treatments have been investigated. It has been found that alloys NiSi20Nb3B0.5, NiS20.4Nb2B0.5, and NiSi20.2Nb2.5B0.5 have acceptable mechanical properties, machinability, and weldability, and have better corrosion resistance in boiling 60%, 70%, and 80% sulfuric acid than any other existing alloys. The effects of Ti, Nb, Cu, Cr, and Mo additions on the microstructure and corrosion resistance of the alloys have been studied. It was found that Ti additions encouraged the formation of the Ni3Si β phase, but the β phase with Ti addition had very poor corrosion resistance. Nb addition increased the ductility and the corrosion resistance of the alloy. Cu, Cr and Mo additions encouraged the formation of the α and γ phases (the former phase usually decreased the corrosion resistance, the latter hurt mechanical properties).
An investigation of the weldability of the alloys showed that the as-cast NiSi20Nb3B0.5 alloy could be successfully welded using 600°C preheat and NiSi20Nb3B0.5 welding rods produced by centrifugal casting. Effects of the G phase (Ni16Si7Nb6) on the corrosion resistance and mechanical properties, corrosion resistance mechanism, and polarization behavior of the alloys were also investigated”--Abstract, page iii.
Newkirk, Joseph William
Kohser, Ronald A.
O'Keefe, T. J. (Thomas J.)
Johnson, James W., 1930-2002
Materials Science and Engineering
Ph. D. in Metallurgical Engineering
University of Missouri--Rolla
xv, 140 pages
Note about bibliography
Includes bibliographical references (pages 136-139).
© 2000 Sanhong Zhang, All rights reserved.
Dissertation - Restricted Access
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Electronic access to the full-text of this document is restricted to Missouri S&T users. Otherwise, request this publication directly from Missouri S&T Library or contact your local library.http://merlin.lib.umsystem.edu/record=b4496689~S5
Zhang, Sanhong, "The development of nickel silicide based alloy for sulfuric acid application" (2000). Doctoral Dissertations. 1338.
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This work was sponsored by Chas. S. Lewis and Co., Inc. in St. Louis.