Research On Synthesis And Mechanical Properties Of Cr-Al-N,Cr-Mo-N Composite Coatings And CrN/Mo₂N Multilayers Coatings

Cr-Al-N composite films, Cr-Mo-N composite films and CrN/Mo₂N multilayer films were prepared by reactive magnetron sputtering technique. Cr-Al-N composite films'microstructure, mechanical and tribological properties influenced by the Al content, Cr-Mo-N composite films'microstructure, mechanical and tribological properties influenced by the Mo content, CrN/Mo₂N multilayer films'microstructure, mechanical and tribological properties influenced by modulation periods, the mechanisms of hardening were investigated. The main conclusions in this work are summarized as follows:The studies on the Cr-Al-N composite films indicated that Cr-Al-N composite films exhibited cubic structure, with (111) preferred orientation. As increasing of Al content, the diffraction peak of c-Cr-Al-N(111) gradually shift to large Angle. When the Al content reached 62.50at.%, h-AlN(100) diffraction peak appeared. As increasing of Al content, grain size became smaller gradually. The maximum hardness of the Cr-Al-N composite films is 41.84GPa when the Al content reached 57.02at.%. Solid solution and internal stress were attributed to the increase of hardness. As increasing of Al content, the friction coefficient and the wear rate of the Cr-Al-N composite films first decreased and then increased.The studies on the Cr-Mo-N composite films indicated that, Cr-Mo-N composite films had a similar face-centered cubic crystal structure of CrN films, and was (111) diffraction peak of preferred orientation. As increasing of Mo content, due to the formation of substitution solid solution, c-Cr-Mo-N (111) diffraction peak gradually shift to small angles. As increasing of Mo content, the hardness of Cr-Mo-N composite films first increased and then decreased. The maximum hardness of the Cr-Mo-N composite films was 33.53GPa when the Mo content was 22.76at.%. The friction coefficient of Cr-Mo-N composite films decreased, while wear resistance gradually increased. It was analyzed that in the friction process Mo reacted and MoO₃ was produced.The studies on the CrN/Mo₂N multilayer films indicated that, the diffraction peaks of the CrN/Mo₂N multilayer films with various modulation periods widened. There was only CrN phase. With the increase of modulation periods, the hardness of CrN/Mo₂N multilayer films first increased and then decreased. The maximum value of hardness is 35.58GPa when the modulation period was 18nm. It was analyzed that the Hall-Petch mechanism didn't play role in the multilayer films, the modulus difference mechanism wasn't main reason and the hardness enhancement was due to the coherence stress mechanism through theoretical calculation. With the increase of modulation period, the friction coefficient of CrN/Mo₂N multilayer films first decreased and then increased. When the modulation period was 18nm, the friction coefficient reached the minimum value 0.4755.