The mechanical behaviour of a polycrystalline silicon carbide across length scales was studied using Vickers indentation, focusing on the hardness, fracture toughness and failure mechanism of the material. For macroscopic and microscopic indentations, the hardness decreased with an increase in load, which was associated with the well-known indentation size effect as well as the internal flaws. For nanoindentation, severe plastic deformation was discovered beneath the imprints on the basal plane (0001) which is the most favourable crystallographic plane for dislocation movement. Alternative sources of plastic deformation, including deformation twinning and stacking faults, were found for nanoindentations with an increased load. Also, cracking was observed for indents made at 100 mN and above, which was used to study the fracture toughness.
Chromium nitride coatings were prepared by reactive DC-superimposed high-power-impulse magnetron sputtering (HiPIMS) system. The influence of substrate bias on the microstructure and mechanical properties of CrN coatings was investigated. XRD and cross-sectional SEM were utilized to characterize the film structures. Mechanical properties were characterized by nanoindentation and Vickers indentation test. The results revealed that the microstructure and mechanical properties of CrN coatings were affected by bias voltage. The CrN coatings exhibited dense and fine columnar grain structure with the hardness of about 18.7 GPa. The fracture toughness of CrN coatings was around 3.16 MPa ⋅ m[Formula: see text]. However, further increase of the bias voltage from −250 V to −300 V led to the degradation of coating properties.
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