Comparison of chromium nitride coatings deposited by DC and RF magnetron sputtering

Chromium nitride coatings were deposited by DC and RF reactive magnetron sputtering on AISI 304 stainless steels without substrate heating. A Cr2N phase was formed in the RF sputtered coatings with a low N2 flow content ranging within 30–50%. A NaCl type CrNx phase was obtained by DC magnetron sputtering with different N2 flow contents. The coating hardness increased with the increase of the N2 flow content. When the coatings deposited with the same N2 flow content were compared, the hardness of the RF sputtered CrNx was higher than that of the DC sputtered CrNx, which was mainly due to the distinct difference between the dense structure (RF process) and the porous structure (DC process). The RF sputtered CrNx coatings showed an excellent adhesion strength as compared to the DC sputtered coatings. By selecting the deposition method and optimizing the N2 flow content, CrNx coatings with a preferred microstructure could be obtained, which would be a candidate material for research and applications in nano-science.