Synthesis and characterisation of self-lubricating tungsten nitride thin films as protective machine tool coatings

ABSTRACT

WN thin films were synthesised on silicon (100) substrate by varying the nitrogen flow rate (NFR) at a substrate temperature of 300°C for the initial 15 min using RF magnetron sputtering. With the increase in NFR from 1.58, 5.29 and 10 sccm (standard cubic centimetres per minute), the FCC β-W₂N phase was converted to mixed phases of FCC β-W₂N and hexagonal δ-WN, and further to amorphous phases. Likewise, XPS results indicated the presence of W-N phases. In addition, structural and morphological studies confirmed the presence of dense films at 1.58 sccm of NFR with a thickness of 430 nm and a surface roughness of 0.99 ± 0.16 nm. Moreover, the film with β-W₂N phase (at 1.58 sccm of N₂ flow) exhibited high hardness and elastic modulus values of 28.36 ± 2.57 GPa and 149.72 ± 8.04 GPa, and better scratch resistance with average coefficient of friction (COF) value of 0.303, making it best suitable for hard coating applications.

KEYWORDS:

• Tungsten nitride
• thin film
• magnetron sputtering
• properties
• coating
• nitrogen flow rate

Acknowledgements

The authors would like to show their gratitude to the Central Instrumentation Facility (CIF), National Institute of Technology Silchar and Central Research Facility (CRF), Indian Institute of Technology Kharagpur for providing a suitable facility to perform the relevant experimentations. It is important to thank Mr. Naveen Kumar Chitturi for his valuable support to successfully complete the experimental investigations.

Disclosure statement

No potential conflict of interest was reported by the author(s).