The influence of nitrogen pressure and substrate temperature on the structure and mechanical properties of CrAlBN thin films

• CrAlBN films were deposited with various nitrogen pressure and substrate temperature.
• The films had a nano-multilayered structure with the nitrogen pressure below 6.67 Pa.
• The hardness of films changed with nitrogen pressure and substrate temperature.
• The maximum hardness of 53 GPa was observed at the substrate temperature of 350 °C.
• Mechanical behavior of CrN/AlBN/CrN systems with various structures of AlBN was simulated.

Thin films of CrAlBN were deposited on SKD 11 tool steel and Si wafer substrates using Cr and Al0.95B0.05 alloy cathodes in a nitrogen gas flow in a cathodic arc process. The influence of nitrogen pressure (PN) and substrate temperature (TS) on the microstructure and mechanical properties of the films was investigated. The CrAlBN films had a nano-multilayered structure in which the nano-crystalline CrN layer alternated with the AlBN layer at the PN below 6.67 Pa. With a further increase of PN, no multilayered structure of the film was observed. The hardness of the films decreased with increasing PN. The films deposited at various TS also had a nano-multilayered structure, but the AlBN layers had an amorphous state at the TS of 250 °C. The hardness of the films increased with the increase of the TS from 250 to 350 °C. Further increase in the TS decreased the hardness. The maximum hardness of 53 GPa was obtained at the TS of 350 °C. A good correlation between the residual stress and the hardness of the films was observed. We also presented the simulation of CrN/AlBN/CrN systems with different structure of AlBN layer. The simulation revealed that the Young's modulus, yield stress and flow stress increased with the increase of the fraction of hexagonal crystal AlBN.