Enhancement of sp3 C Fraction in Diamond-like Carbon Coatings by Cryogenic Treatment

Abstract

Diamond-like carbon (DLC) coatings deposited onto high-speed-steel surfaces were subjected to deep cryogenic treatment (DCT) at temperatures of −120 to −196 °C to investigate the evolution of microstructure, bonding structure, and mechanical properties. The surface morphology and the bonding structure of the DLC coatings were studied using scanning electron microscopy, transmission electron microscopy, micro-Raman spectroscopy, and X-ray photoelectron spectroscopy. It is found that DCT affects the surface morphology, especially the size and the height of the aggregates. For those DLCs with more than 50% sp3 C fraction, the sp2 C → sp3 C transformation occurred in coatings treated at a temperature of −120 to −160 °C; and the maximum fraction of sp3 C was obtained after treatment at −140 °C. Almost keeping the wear resistance of DLCs, DCT can improve the adhesion strength, and surface hardness. The findings of this study indicate that DCT will be a potential post-treatment method to tune the microstructure and mechanical performance of DLC coatings.

Functional Surface Coatings on Orthodontic Appliances: Reviews of Friction Reduction, Antibacterial Properties, and Corrosion Resistance

“…There is still room for improvement of this excellent performance of DLC coatings. For example, deep cryogenic treatment (DCT) at temperatures from −120 to −196 °C can improve adhesion strength from 30.08 N to up to 40.54 N [ 180 ]. Therefore, this post-treatment method may be a potential way to improve wear resistance.…”

“…DLC coatings, in turn, have the ability to reduce friction [ 80 ] and are more biocompatible [ 178 , 179 ]. Although the application of DLC coatings leads to a decrease in the surface hardness of the attachments, this can be enhanced and the corrosion resistance further increased by means of DCT [ 180 ].…”

Duplex Surface Modification of 304-L SS Substrates by an Electron-Beam Treatment and Subsequent Deposition of Diamond-like Carbon Coatings

“…It is well known that the sp 2 hybridization represents one s orbital and two p orbitals, creating three new hybrid sp 2 orbitals with equal energy, and correspond to a graphitic structure. Similarly, in sp 3 hybridization, one s and three p orbitals form four new hybrid sp 3 orbitals and correspond to a diamond structure [15].…”