Syntheses and mechanical properties of Cr–Mo–N coatings by a hybrid coating system

Effects of Mo content up to 30.4 at.% on the microstructure and mechanical properties of CrN coatings are reported in this study. Ternary Cr–Mo–N coatings were deposited onto steel substrates (AISI D2) using a hybrid coating method of arc ion plating (AIP) using Cr target and DC magnetron sputtering technique using Mo target in N 2/Ar gaseous mixture. The synthesized Cr–Mo–N coatings formed a substitutional solid solution of (Cr,Mo)N where larger Mo atoms replaced Cr in CrN crystal. The Cr–Mo–N coatings showed increased hardness value of approximately 34 GPa at 21 at.% Mo, compared with 18 GPa for pure CrN. The friction coefficient decreased from 0.49 for pure CrN coating to 0.37 for Cr–Mo–N with 30.4 at.% Mo. This result is believed to be due to tribo-layer formation of MoO 3 which is known to function as a solid lubricant.