THE X-RAY CHARACTERIZATION OF THE ION--PLATED MULTILAYER
COATINGS
S.Betsofen,L.Petrov, R.Ronyak
Inst.of metallurgy RAN,Leninskyi pr.49, 117334
Moscow,Russia
A complex approach to the problem of formation of
multilayer ion -plated
coatings has been developed. It includes the optimization of sputtering
technology by
monitoring of structure features:
- crystallographic orientation of layers and the type of interface layer;
- thickness of layers
- the value and sign of residual macrostresses.
The stability of coating properties is provided by
development of the coating
characterization methods :
- the precious x -ray fluorescence method
for measurement
of coating thickness in a polylayer coatings with accuracy 0,1 mm;
-
the measurement
of crystallographic texture of layers by pole figure and inverse pole
figure method;
-
the calculation of residual macrostress taking account for both the texture and elastic
anisotropy ;
-
the determination of macrostress nonuniformity;
- the method of true
microhardness determination for thin coatings taking account for both coating
thickness and of substrate microhardness.
Investigation of coating structure as a function of sputtering technology shows that
variations in arc current and nitrogen pressure lead to the different crystallographic
orientations of TiN layers.These orientations vary in the range from {110} for low of
both nitrogen pressure and arc current to {111} for higher values of its. Variations in
arc current and nitrogen pressure lead to the different types of the interface between Ti
and TiN layers from diffuse type to coherent type.The predominant orientations o@_ Ti
interlayer are observed: { 1 0 1 0}, { 1 1 20} and { 1 0 1 1 } in the case diffuse interface. In the
case coherent interface the texture of Ti interlayer is characterized by single component
{0001}. This texture is caused by the epitaxial grow of Ti crystals on the
TiN
underlayer with texture {1 1 1} and by realization of the orientation relationship:
{000 1 }$_{Ti}$ || { 1 1 1}$_{TiN}$. Above mentioned two mechanism of
formation polylayer
coatings lead to a difference in coating performance. In the case of coherent interface
are observed the spallation effect in the flattened cylindrical
specimens.
The features of macrostress measurements concern
with thin high textured
coatings are considered. It is shown that the dependence e
vs.$\sin^{2}$y concerns to linear
and nonlinear forms.The contribution of both the texture and elastic anisotropy to the
macrostress measurements are calculated in terms of elastic anisotropy theory. The
indexes of x -ray reflections for which elastic anisotropy lead to linear or nonlinear
dependencies e vs. $\sin^{2}$y are determined. It is shown that TiN coatings have a
nonuniform distribution of macrostresses in grains with different orientation and the
grains belonging to the main texture component have the highest level of residual
macrostress. The level of nonuniformity can be controlled by variations of sputtering
parameters. These results may be used in practice: (1) for the improving of the
sputtering technology; (2) for the process monitoring; (3) for the comparative
determination of the microstructure state of the coatings are obtained by different
sputtering methods.