Using the PVD arc ion plating method, Cr-B-N, Cr-C-N, and Cr-O-N coatings with different B, C, and O contents, and CrN coatings were prepared. Their microstructures and some properties were also investigated.
X-ray diffraction measurements revealed that all the coatings have the NaCl type cubic CrN phase. Other phases such as boride, carbide, and oxide were not detected. Because of the addition of the third element to the CrN coating, the diffraction peaks shifted to a lower angle and the peaks broadened.
As the amount of the third element increased, hardness of Cr-B-N, Cr-C-N, and Cr-O-N coatings increased because the grain sizes became smaller and the compressive residual stresses increased. Results showed that, even with small amounts, the addition of B had the greatest influence on high hardness and high residual stress.
TEM observations revealed that the CrN coating has a dense columnar microstructure, and that the addition of the third element makes the grain sizes smaller than that of the CrN coating. Results show that the Cr-B-N coating has the smallest grains, and that the fine microstructure exhibits good correlation with its properties.

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