Effect of Ni doping on the microstructure and toughness of CrAlN coatings deposited by magnetron sputtering

This study determines the effects of nickel (Ni) doping on the composition, phase structure, chemical valence state, hardness, and toughness of CrAlNiN coatings. CrAlNiN coatings with various Ni contents (0.00 at.%-27.71 at.%) were deposited on the surfaces of M2 tool steel and monocrystalline silicon (Si) using unbalanced magnetron sputter ion plating. The results showed that the CrAlNiN coatings possess a nanomultilayer structure, maintaining the face centered cubic crystal structure of the chromium aluminum nitride (CrAlN) coatings. The Ni in the coatings acts as a toughening phase to ease stress, to increase resistance to crack growth, and to delay the generation of cracks, thereby having an obvious toughening effect. At an Ni content of approximately 20.33%, the Ni toughening phase in the modulation layer tends to saturate and the effect of continuing the increase in Ni content is limited from the viewpoint of improving the toughness.