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

¹ Department of Intelligent Mechanical Systems, Tokyo Metropolitan University, Tokyo, Japan
² BIAS – Bremer Institut für angewandte Strahltechnik, Bremen, Germany
³ Faculty of Production Engineering-Mechanical Engineering & Process Engineering, University of Bremen, Bremen, Germany

^* Corresponding author : simizu-tetuhide@tmu.ac.jp

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.