E. Schaffer et G. Kleer, Mechanical behavior of (Ti,Al)N coatings exposed to elevated temperatures and an oxidative environment, SURF COAT, 133, 2000, pp. 215-219
TiAlN coatings were deposited in an ion beam-assisted deposition process on
silica substrates with Variations in the deposition parameters, particular
ly the ion energies. For these coatings the residual stress after depositio
n and its temperature dependence was determined. In order to study the infl
uence of oxidation, the residual stress was also analyzed after exposing sp
ecimens to air at temperatures up to 650 degreesC. For the characterization
of the stability and the mechanical behavior, scratch tests were performed
on coatings having different initial stresses, before and after the exposu
re treatments. It was found that for coatings with compressive stress betwe
en 1000 and 6000 MPa, the critical loads determined in the scanning scratch
tests exceeded the values observed for tensile-stressed coatings by more t
han three-fold. Exposing the coated specimens to hot air led to changes in
the residual stress, e.g. to a decrease in the compressive stress from 5700
to 3300 MPa after 1 h at 600 degreesC, and also to a decrease in the mecha
nical stability; for such coatings for example, a drop in the critical load
by up to 50% after 1 h at 600 degreesC in air was observed. (C) 2000 Elsev
ier Science B.V. All rights reserved.