Microstructural, mechanical and wear properties of Cr-Al-B-N coatings deposited by DC reactive magnetron co-sputtering

Nanocomposite Cr-Al-B-N thin films were deposited on a p-type (100) silicon wafer substrate with different chemical compositions by designing different distances from the magnetron sources. The Al and Cr-B (20 at.% B) alloy targets were co-deposited using DC reactive magnetron sputtering in the presence of the reactive gas mixture were conducted. The chemical composition effects on the microstructural, mechanical, wear and mold-releasing properties of the Cr-Al-B-N films were investigated. The experimental results indicate that the Cr-Al-B-N coatings exhibit a nanocomposite structure of nanocrystalline (Cr, Al)N, a soft amorphous BN matrix and a small quantity of oxides, similar to the Cr-B-N or Cr-Al-Si-N structure. Specimen #6 of Cr0.27Al0.1B0.21N0.42 film exhibited the highest hardness of 18 GPa and H-3/E-2 ratio of 0.21 GPa resulting from the stoichiometric and phase volume fraction effects on the nanocrystalline structure. Wear test results show that the Cr-Al-B-N film has a variable coefficient of friction with values between 0.5 and 0.7, which strongly depends on the BN volume fraction. Moreover, a decrease in the surface roughness leading to an increase in the contact angle was related to an increase in the BN amorphous matrix volume fraction in Cr-Al-B-N films. Compared to the CrN film, the contact angle of the Cr-Al-B-N films was improved by up to 17%-40% owing to the increase in surface tension. Therefore, the results of this study show potential possibility in field of mold-releasing applications in the future. (C) 2010 Elsevier B.V. All rights reserved.