# High-Vacuum Tribological Behaviors of Wear-Resistant WC/a-C:H Coatings with Strong Adhesion on Zirconia

## TL;DR

This study improves the performance of zirconia in high-vacuum environments by using a special coating that resists wear and adheres strongly to the material.

## Contribution

A novel WC/a-C:H coating with Cr ion implantation is introduced for enhanced adhesion and wear resistance on zirconia in high-vacuum conditions.

## Key findings

- The WC/a-C:H coating on Cr-implanted zirconia showed 112% higher adhesion strength compared to unmodified zirconia.
- The coating exhibited high friction coefficient and excellent wear resistance across a wide load range in high vacuum.
- Compared to zirconia self-mated pairs, the coating reduced wear rates by 1-2 orders of magnitude.

## Abstract

To improve the applicability of tetragonal zirconia (TZP) in the high-vacuum friction drive field, a strategy combining Cr ion implantation-modified layer and hydrogen-containing amorphous carbon coating was proposed in this study. The designed coating (WC/a-C:H) consists of a Cr bonding layer, a WC-rich load-bearing layer and an a-C:H target layer. The effects of implantation voltage on the adhesion strength of WC/a-C:H coatings were investigated. The tribological behaviors of WC/a-C:H against TZP and TZP self-mated pairs at various loads in high vacuum were comparatively explored. The results indicated that when the TZP substrate was modified by a Cr ion implantation layer, the WC/a-C:H coating showed obviously better adhesion strength. Therein, at the implantation voltage of 30 kV, the coating exhibited the optimal adhesion of 88 N, which was 112% higher than that of the coating on original TZP. Surprisingly, the WC/a-C:H coating featuring maximum adhesion strength also achieved a high friction coefficient (>0.22) and exceptional wear resistance across a wide load range of 0.5~15 N in high vacuum. Compared with the TZP self-mated wear pairs, the wear rates of both the WC/a-C:H coating and its counterparts decreased by 1~2 orders of magnitude. Unlike the severe abrasive wear and plastic deformation of the TZP self-mated pairs, even at 15 N, the WC/a-C:H coating exhibited mild abrasive wear and adhesive wear mechanisms.