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 H3/E2 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.