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

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 (P-N) and substrate temperature (T-S) 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 P-N below 6.67 Pa. With a further increase of P-N, no multilayered structure of the film was observed. The hardness of the films decreased with increasing P-N. The films deposited at various T-S also had a nano-multilayered structure, but the AlBN layers had an amorphous state at the T-S of 250 degrees C. The hardness of the films increased with the increase of the T-S from 250 to 350 degrees C. Further increase in the T-S decreased the hardness. The maximum hardness of 53 GPa was obtained at the T-S of 350 degrees 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. (C) 2013 Elsevier B. V. All rights reserved.