Microstructural and mechanical properties of graded and multilayered AlxTi1-xN/CrN coatings synthesized by a cathodic-arc deposition process

Graded and multilayered AlxTi1-xN/CrN coatings were synthesized by cathodic-arc evaporation (CAE) with plasma enhanced duct equipment. Chromium and AlTi alloy cathodes were used for the deposition of AlxTi1-xN/CrN coatings. During the coating process of graded AlxTi1-xN/CrN, an Al0.63Ti0.37N top layer was deposited on an interlayer of Al0.63Ti0.37N/CrN, which was obtained by regulation of cathode power. With different cathode current ratios (Al0.67Ti0.33/Cr) of 0.75, 1.0, and 1.33, the deposited multilayered Al0.63Ti0.37N/CrN coatings possessed different chemical contents and periodic thicknesses. The nanolayer thickness and alloy content of the deposited coating were correlated with the evaporation rate of alloy cathode materials. Periodic thickness and layer thickness ratio of Al0.63Ti0.37N/CrN increased with increasing I[AlTi]/I[Cr] cathode current ratio. High resolution transmission electron microscopy showed that lattice distortion and dislocations are found at the interface between Al0.63Ti0.37N and CrN layers in the multilayered Al0.63Ti0.37N/CrN. Hardness enhancement is a consequence of dislocation blocking. The multilayered Al0.63Ti0.37N/CrN coatings possessed higher hardness (35–36 GPa) and better fracture toughness (KIC = 1.65–2.05 MPa m1/2) than those of the graded Al0.63Ti0.37N/CrN.