Geometrical design of micro-textured DLC coatings toward lubricant-free metal forming

Tetsuhide Shimizu,Hamza Messaoudi,Ming Yang,Hironori Kan,Frank Vollertsen,F Vollertsen,T.A Dean,S.J Yuan,Y Qin

doi:10.1051/matecconf/201819013001

Abstract

To achieve a stable and high wear resistive functional surface under dry sliding friction, the present study proposes micro-textured diamond like carbon coatings fabricated by ionized physical vapour deposition (I-PVD) using metallic masks. To clarify the optimized geometrical dimensions under dry sliding friction, geometrical conditions of textured array patterns are varied by using metallic masks with different circular hole array patterns fabricated by picosecond pulsed laser processing. The effect of texturing on friction and wear properties is evaluated by ball-on-disk type friction tests for the condition of a constant DLC-coverage per unit area. Thereby, textured DLC pattern with diameters of 50 μm, 100 μm and 150 μm are applied. Within the first 10,000 laps stable and lower coefficient of friction is obtained with the smallest diameters of 50 μm. However, at further rotation of more than 40,000 laps, the wear of the smaller diameters becomes more pronounced due to the increase of stress concentration at the edge of the structure. Based on these findings, geometrical design of micro-textured DLC coating is discussed with regard to the suppression of three-body ploughing and the prevention of stress concentration.

Highlights

With the growing awareness of environmental issues, the efforts towards a lubricant-free metal forming are intensifying [1]
The first step in this work was the manufacture of the metallic masks following the design required for the subsequent diamond like carbon (DLC)-deposition
For the design of micro-texture that fulfil the requirements of a durable dry sliding, the balance between the efficient ejection of wear debris from contact interface, which can be realized by scaling down of the apparent contact area, and the suppression of the stress concentration by decreasing the interspace to distribute the stress with surrounding textures represent the key parameters to determine the geometrical dimensions

Summary

Introduction

With the growing awareness of environmental issues, the efforts towards a lubricant-free metal forming are intensifying [1]. In particular under the plastic deformation of the work materials, as it is the case within a metal forming operation, wear debris of various sizes is generated and the trapped particles at the interface induce a three-body ploughing behaviour, which significantly increases the friction and its large deviations [3]. A down scaling of the apparent contact area can help in reducing the three-body ploughing effect For this purpose, functionalized surfaces are required. To realize stable dry friction conditions, the authors proposed an application of surface texturing with micro structured diamond like carbon (DLC) coatings to decrease the apparent contact area during sliding [6]. Based on the comparison of tribological properties between different texture dimensions, geometrical design of micro-textured DLC coatings towards lubricant-free metal forming is discussed

Picosecond laser fabrication of metallic masks

Ionized physical vapour deposition of DLC films

Tribological evaluations

Laser manufactured metallic masks

Fabrication of micro-textured DLC films

Conclusions