Low friction characteristics and tribochemistry analysis of novel AlTiN/a-C based nanocomposite coatings

• Published in: Applied surface science Vol. 678; p. 161137
• Main Authors: Dinesh Kumar, D., Kirubaharan, Kamalan, Panda, Kalpataru, Kuppusami, P., Arivarasan, A., Stimpel-Lindner, Tanja, Duesberg, Georg S.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.12.2024
• Subjects: a-C; Graded coatings; Low friction; sp2/sp3 carbons; Tribochemistry; Wear resistance; Graded coatings; Tribochemistry; Low friction; Wear resistance; sp2/sp3 carbons; a-C
• ISSN: 0169-4332
• DOI: 10.1016/j.apsusc.2024.161137

[Display omitted] •Newly developed compositionally graded AlTiN/a-C nanocomposite coatings using magnetron sputtering.•Evaluation of tribological properties were carried out under room temperature and 673 K.•Enhanced tribological performance were observed for compositionally graded coatings because of its refined microstructure.•Tribochemistry analysis of wear surfaces of all the coatings were carried out using XPS. Friction reduction of AlTiN-based hard coatings is gaining much attention among researchers worldwide to broaden their tribological applications. Metal/non-metal inclusions, as well as the design of a novel coating architecture, are primarily focused on reducing friction while retaining wear resistance. This study investigates the tribological characteristics of magnetron sputtered AlTiN coatings by incorporating amorphous carbon (a–C) at different concentrations (5–25 at.%), as well as the compositionally graded AlTiN/a-C coatings (CGC). The XPS and Raman spectroscopy results confirm the presence of a-C features, while XRD reveals the formation of ceramic carbide phases in AlTiN coatings with higher carbon content and CGC coatings. The CGC AlTiN/a-C have shown a maximum hardness of 34.3 GPa and an elastic modulus of 321 GPa due to their refined grain structure. The CGC had the lowest friction (0.18 at 300 K and 0.37 at 673 K), as well as improved wear resistance (2.74 × 10−7 mm3/Nm (300 K) and 4.93 × 10−7 mm3/Nm (673 K)). The tribolayers are found to be mainly composed of sp2/sp3 bonded a-C features (including C=C/C─C, C─N, and C─O), which reduces the friction force significantly. The CGC AlTiN/a-C coating has exhibited improved wear resistance behavior due to their finely grained structure and improved mechanical properties.