Corrosion of Titanium Matrix Composites Page: 1 of 7

DOE/ARC-02-011
Corrosion of Titanium Matrix Composites
Bernard S. Covino, Jr. and David E. Alman
Albany Research Center, U.S. Department of Energy, Albany, OR USA
Abstract
The corrosion behavior of unalloyed Ti and titanium matrix composites containing up to 20
vol% of TiC or TiB2 was determined in deaerated 2 wt% HCl at 50, 70, and 90 C. Corrosion
rates were calculated from corrosion currents determined by extrapolation of the tafel slopes.
All curves exhibited active-passive behavior but no transpassive region. Corrosion rates for
Ti + TiC composites were similar to those for unalloyed Ti except at 90 C where the
composites were slightly higher. Corrosion rates for Ti + TiB2 composites were generally
higher than those for unalloyed Ti and increased with higher concentrations of TiB2. XRD
and SEM-EDS analyses showed that the TiC reinforcement did not react with the Ti matrix
during fabrication while the TiB2 reacted to form a TiB phase.
Keywords: titanium, composite, particulate, titanium carbide, titanium diboride
Introduction
Titanium and its alloys have low density and high strength, stiffness, and creep and corrosion
resistance. Titanium-based composites have current applications in non-aerospace
applications such as industrial, automotive, and consumer [1-5]. Some areas of use for
titanium based alloys and composites are steam turbine blades, coal transport systems,
automotive springs, valve spring retainers and valves, and consumer eyeglass frames,
cooking ware, and bicycles. Particulate-reinforced titanium matrix composites are being
considered for wear resistant (gears, bearings, shafts), erosion and corrosion resistant
(tubing), and creep resistant (engine) applications [5].
The purpose of this paper is to determine the effect of different particulate reinforcements
(TiC and TiB2) at several concentrations affect the corrosion behavior of titanium matrix
composites. The wear behavior of those composites has been published elsewhere [6] and
shown to correlate well with particulate concentration and microhardness. That is, as the
particulate concentration increases, the microhardness increases and the wear rates decrease.
Ti + TiB2 composites had lower wear rates than Ti + TiC composites in similar environments.
While the wear properties have been well characterized, however, little is known about their
corrosion properties. Research presented here will report the effect of a reducing acid
(deaerated 2 wt% HCl) at several temperatures on the corrosion of all constituents of the
composite.
Experimental
Titanium powder was dry blended with 0, 2.5, 5, 10, and 20 volume percent (vol%) TiC or
TiB2. All powders were commercially available and were -325 mesh (-44 :m in size).
Blending of the powders was accomplished in glass jars using a turbula type mill.
Rectangular, green composite powder billets (approximately 19 mm X 19 mm X 254 mm)

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Covino, B.S., Jr. & Alman, D.E. Corrosion of Titanium Matrix Composites, article, September 22, 2002; (digital.library.unt.edu/ark:/67531/metadc780332/m1/1/ocr/: accessed November 17, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.

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