# Tailoring the Microstructure and Properties of HiPIMS-Deposited DLC-Cr Nanocomposite Films via Chromium Doping

## TL;DR

This paper shows how adding chromium to diamond-like carbon films can improve their mechanical and tribological properties for engineering uses.

## Contribution

The study demonstrates controlled chromium doping in DLC films using HiPIMS to optimize mechanical and tribological performance.

## Key findings

- Chromium doping increases hardness and elastic modulus at optimal levels but reduces mechanical strength at higher concentrations.
- Moderate Cr doping significantly lowers friction coefficient and wear rate, enhancing tribological performance.
- Surface wettability improves with Cr doping, as shown by reduced water contact angles and increased surface energy.

## Abstract

Chromium-doped diamond-like carbon (DLC-Cr) nanocomposite films were successfully deposited using a high-power impulse magnetron sputtering (HiPIMS) system. The Cr content in the films was controlled by adjusting the Cr target powers. The influence of Cr content on the microstructure, mechanical properties, tribological performance, and wettability of the films was systematically investigated. The results show that the Cr content and deposition rate of the films increased with increases in the target power. The surface topography of the films evolved from smooth to rough as the Cr target increased from 10 W to 70 W. At low Cr doping rates, the film mainly exhibited an amorphous structure, whereas the nanocomposite structure was formed at proper Cr doping rates. Raman and XPS analyses revealed that Cr incorporation altered the ID/IG ratio and promoted the formation of Cr-C bonds, leading to a more graphitic and nanocomposite-like structure. The nanoindentation results show that an optimal Cr content enhances both hardness and elastic modulus, while higher Cr concentrations lead to a decline in mechanical strength due to more graphitization and decreasing stress. Tribological tests exhibited a significant reduction in the friction coefficient (0.21) and wear rate (0.63 × 10−14 m3/N·m) at a moderate Cr level. Additionally, the surface wettability evolved toward enhanced hydrophilicity with increasing Cr power, as evidenced by reduced water contact angles and increased surface energy. These findings demonstrate that controlled Cr incorporation effectively tailors the structure, stress state, and surface chemistry of DLC films, offering a tunable pathway to achieving optimal mechanical performance and tribological stability for advanced engineering applications.