Title: Femtosecond laser assisted generation of micro-dimples on moly-chrome film for improving its tribology

Authors: V. Ezhilmaran; N.J. Vasa; L. Vijayaraghavan; Sivarama Krishnan

Addresses: Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, 600036, India ' Department of Engineering Design, Indian Institute of Technology Madras, Chennai, 600036, India ' Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, 600036, India ' Department of Physics, Indian Institute of Technology Madras, Chennai, 600036, India

Abstract: Femtosecond laser ablation of the moly-chrome deposited piston ring and the influence of laser fluence and number of laser pulses on dimple morphology and geometry were analysed. The increase of laser fluence and pulse numbers beyond 8.4 J/cm2 affected the dimple surface by inducing severe cracks due to heat accumulation. Based on the experimental investigation, the ablation threshold for moly-chrome film was found to be 0.36 J/cm2. Textured surface was formed on the moly-chrome film with laser fluence near the ablation threshold and the tribological characteristics were studied. The piston ring surface was textured with dimple diameter of 100 μm and dimple aspect ratio of 0.2. Effect of different dimple area ratios, such as 2%, 16% and 38% were analysed by reciprocating type tribology testing. The textured surface with 16% dimple area ratio showed a reduction in friction compared to the plain and the remaining textured piston rings.

Keywords: surface texturing; micro-dimple; tribology; friction; femtosecond laser.

DOI: 10.1504/IJPTECH.2019.100909

International Journal of Precision Technology, 2019 Vol.8 No.2/3/4, pp.261 - 278

Available online: 09 Jul 2019 *

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