H. Mitsui et al., THE SULFIDATION AND OXIDATION BEHAVIOR OF SPUTTER-DEPOSITED AL-TA ALLOYS AT HIGH-TEMPERATURES, Corrosion science, 39(1), 1997, pp. 59-76
As a part of a systematic study to elucidate oxidation and sulfidation
resistance of Al-refractory metal alloys at high temperatures, the be
havior of sputter-deposited Al-(33-80) at.%Ta alloys has been examined
at temperatures ranging from 1073 K to 1273 K in HeS2 atmosphere and
in Ar-O-2 atmosphere. The sulfidation kinetics of these alloys follow
a parabolic rate law in an early sulfidation stage, although, in some
cases, the sulfidation rates are decreased after prolonged sulfidation
. The sulfidation resistance of these alloys is comparable to that of
high purity tantalum and remarkably higher than those of typical high
temperature alloys. The sulfide scales on these alloys comprise an out
er aluminum-rich layer and an inner tantalum-rich layer. The formation
of a protective inner tantalum sulfide layer is responsible for the e
xcellent resistance to high temperature sulfidation. The oxidation kin
etics of the Al-Ta alloys change with alloy composition and temperatur
e. The oxidation of Al-33Ta initially follows a parabolic rate law, bu
t after a particular period of oxidation, rapid oxidation is observed
at high temperatures above 1173 K. In contrast, the oxidation rates of
higher tantalum alloys decrease with oxidation time, although the oxi
dation rates in the early stage are higher than those of Al-33Ta. At t
he temperatures below 1123 K a rapid weight loss during oxidation was
observed for the Al-Ta alloys. This seems to result from disintegratio
n of these alloys due to the pest phenomenon. Copyright (C) 1996 Elsev
ier Science Ltd