Factors governing the mechanical behaviour of CrSiN coatings: Combined nanoindentation testing and transmission electron microscopy

Wo, P.C., Munroe, P.R., Li, Z., Jiang, Z-T, Xie, Z.H., Zhou, Z.F. and Li, K.Y. (2012) Factors governing the mechanical behaviour of CrSiN coatings: Combined nanoindentation testing and transmission electron microscopy. Materials Science and Engineering: A, 534 . pp. 297-308.

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Abstract

A direct link between the microstructure and mechanical properties of CrSiN coatings with varying Si contents
was established by examining their microstructural evolution and deformation behaviour, enabled
by cross-sectional transmission electron microscopy. A transformation from a columnar-grained structure,
in the binary compound, to a nanocomposite structure, consisting of CrN nanocrystallites embedded
in an amorphous matrix, was observed in the coating having a Si content of 28.5 at.%. The columnarstructured
coatings were observed to deform by grain boundary shear sliding, whilst cracks occurred
in nanocomposite coatings. Moreover, the coating having a Si content of 14.3 at.% exhibited the highest
hardness as a result of grain boundary strengthening facilitated by Si3N4 segregation, together with solid
solution strengthening of Si in CrN, the Hall–Petch effect for the finer CrN grains and a high compressive
residual stress. A further increase of Si content to 28.5 at.% led to a reduction in hardness due to the high
volume fraction of the amorphous phase, together with the presence of cracks in the as-deposited coating.
The findings provide deeper insight into the origin of the mechanical behaviour of CrSiN coatings.