A full characterization of amorphous or nanostructured coatings at the
microstructural level has some intrinsic difficulties associated with the
lack of long range order and reference compounds, which often make difficult
their study. Only by the combination of different characterization
techniques is possible in many cases to achieve valuable chemical and
structural information.
In this paper, three different systems were used to illustrate how the
combination of characterization techniques, as TEM associated to ED or EELS,
EFTEM, SEM, XPS, RBS and XRD was determinant to correlate microstructure
with deposition parameters and properties in such complex systems. The
coatings were deposited on silicon and AISI M2 steel substrates by magnetron
sputtering under different Ar/N2 gas mixtures from Ti and C targets
(system 1 and 2) or a Si target (system 3). In each case, the performed
characterization allowed to get a deeper understanding of the whole system
and explain their mechanical response. The studied systems are:
(i) Ti-TiN-CN
x
multilayered coatings: the chemical and structural
analysis shows that a gradual enrichment in nitrogen and nitride phases from
the metallic substrate to the CN
x
top layer is responsible for the
improvement of the adhesion properties.
(ii) Ti-C-N: the existence of a nanocrystalline TiC phase embedded in an
amorphous carbon matrix is demonstrated by the microstructural and chemical
analysis for samples prepared under pure Ar. When N2 is introduced in
the gas phase, the nanocrystalline structure is not seen and the chemical
composition is enriched in amorphous non-stoichiometric CN
x
.
(iii) SiO
x
N
y
: although the coatings present similar composition,
small differences in microstructure are observed, which can be responsible
for different mechanical properties.