Effects of silicon doping on low-friction and high-hardness diamond-like carbon coating via filtered cathodic vacuum arc deposition

Jisoo Kim,Young-Jun Jang,Jae-Il Kim,Jongkuk Kim

doi:10.1038/s41598-021-83158-4

Jisoo Kim, Young-Jun Jang + Show 2 more

Open Access

https://doi.org/10.1038/s41598-021-83158-4

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Abstract

In this study, silicon (Si) was doped on a tetrahedral amorphous carbon (ta-C) coating and the tribological characteristics of the resulting Si-doped diamond-like carbon (DLC; a-C:Si:H) were investigated against a SUJ2 ball. The Si fraction in the coating was varied from 0 to ~ 20 at.% by increasing the trimethylsilane gas flow rate during filtered cathodic vacuum arc deposition. The coefficient of friction (CoF) showed no obvious change when the Si fraction was less than ~ 7 at.%. However, after Si doping, it significantly decreased when the Si fraction was greater than ~ 8 at.%. The running-in period also decreased to less than 1000 cycles after Si doping. The rapid formation of Si-rich debris and transfer layer led to the fabrication of a low-friction tribofilm, which was induced by the tribochemical reaction with moisture under ambient conditions. When the Si fraction was ~ 17 at.%, the lowest CoF of less than 0.05 was obtained. Further Si doping beyond the critical point led to the destruction of the film because of reduced hardness.

Highlights

In this study, silicon (Si) was doped on a tetrahedral amorphous carbon coating and the tribological characteristics of the resulting Si-doped diamond-like carbon (DLC; amorphous carbon with hydrogen (a-C):Si:H) were investigated against a SUJ2 ball
A decrease in the surface roughness could be attributed to the change in the deposition mechanism and a shorter processing time, which resulted in a higher deposition rate when the TMS gas was used for doping Si on the DLC coating
When filtered cathodic vacuum arc (FCVA) was used without the TMS gas for pure tetrahedral amorphous carbon (ta-C) deposition, ionized carbon plasma was directly deposited on the surface of WC samples

Summary

Introduction

Silicon (Si) was doped on a tetrahedral amorphous carbon (ta-C) coating and the tribological characteristics of the resulting Si-doped diamond-like carbon (DLC; a-C:Si:H) were investigated against a SUJ2 ball. When the TMS gas flow rate was increased from 0 to 12 sccm, the roughness decreased from 0.06 μmRq to 0.008 μmRq. the peak-to-valley distance (Rt) clearly decreased from 1.14 μmRt to 0.22 μmRt. This reduction in the surface roughness could effectively decrease the abrasive friction and wear, thereby eliminating mechanical interlocking. A decrease in the surface roughness could be attributed to the change in the deposition mechanism and a shorter processing time, which resulted in a higher deposition rate when the TMS gas was used for doping Si on the DLC coating.

Results

Conclusion