Nanoindentation induced plastic deformation in nanocrystalline ZrN coating

• Microstructure evolution of nano-indented zone of ZrN was investigated.
• Dislocation glide, crack initiation and propagation result in the deformation.
• Intergranular fracture by crack propagation along the GBs was found.

Microstructure evolution of nano-indented zone of nanocrystalline ZrN coating has been investigated by transmission electron microscopy. Dislocation glides together with microcrack initiation and propagation contribute to the plastic deformation of the ZrN coating. The dislocation density of the deformed zone reaches ~3×1012 cm−2. The microcracks preferentially initiate just underneath the contact surface and then propagate along the columnar yet weak bonded grain boundaries. The microcrack propagation is found to be the probable factor deteriorating the coating hardness. Strategy to improve the coating hardness via strengthening the grain boundaries has been discussed.

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