1:30pm - 1:45pm
Friction reduction of stainless steel surfaces by laser microstructuring
1Photonik-Zentrum Kaiserslautern e. V. (PZKL), Germany; 2EPflex Feinwerktechnik GmbH, Germany
Recently, friction reduction has become important in a wide range of technical applications. One limiting factor is the abrasion of two surfaces when they are moved against each other, causing friction losses. To overcome this, a functional optimization is necessary and thus the effectiveness of components will be increased by structuring the surfaces. Our approach is to introduce a dimple structure by laser microstructuring into the surface and thus significantly reduce the friction. In order to avoid burr around these dimples it is necessary to operate good heat management. For this reason, we carried out experiments using a USP laser with a pulse duration of 10 ps. Dimples with a diameter of 10 - 30 micrometers were made and systematic investigations were carried out by changing the depth and the arrangement of the dimples. By optimizing these parameters, friction could be reduced by 30 % compared to an unstructured surface.
1:45pm - 2:00pm
Impact of confined laser plasma plumes on the formation of LIPSS structures on stainless steel 316L
1The University of Manchester, United Kingdom; 2Waters Plc, United Kingdom
Laser-induced periodic surface structures (LIPSS) has been used for functionalisation of the surface. Hence, the control of the formation of the LIPSS structures is considered an important feature. In this work, picosecond pulsed laser irradiation (wavelength 355nm, pulse duration 10ps, frequency 404.7 kHz) were performed on stainless steel 316L under the conditions of confined laser plasma plumes in an air environment. The plasma plumes generated due to laser-metal interaction were confined by covering the metal surface with a transparent glass plate at varying distances (Δz = 0, 150, 300, 450, 900 μm). The impact of the gap between metal and glass surface, towards the formation of uniform high-spatial-frequency-LIPSS (HSFL) was studied experimentally. Additionally, low-spatial-frequency-LIPSS (LSFL) was observed at higher fluence along with scattered metal deposits on the surface. This work demonstrated the possibility of creating uniform HSFL using confined laser plasma plumes as the impacting medium.
2:00pm - 2:15pm
Surface carbon enrichment of stainless steel using nanosecond pulsed laser surface alloying of graphite based coating
Chair of Laser Processing, Department of Mechanics of Solids, Surfaces & Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE, Enschede, the Netherlands
Laser surface alloying is a promising technique for modifying and/or improving surface properties of forming tools used in the fabrication thermoplastic composite parts. In this article, the results of a study on laser surface alloying of graphite based coatings on ferritic stainless steel using a nanosecond laser source is presented. The effect of different laser processing parameters and coating types on the laser-induced carbon diffusion are analyzed. The morphology of the processed areas was characterized using confocal microscopy and scanning electron microscopy. The atomic concentration of diffused carbon was determined using energy-dispersive X-ray spectroscopy. It was found that the surface carbon content of stainless steel can be increased substantially up to 70%. Cross-sectional analysis revealed the dependence of diffusion thickness on accumulated laser fluence, having a maximum at 6 µm. In comparison with low and high carbon steel, and unprocessed stainless steel, laser processed samples demonstrated improved wear properties.
2:15pm - 2:30pm
The effect of chemical components on wettability at ps laser micromachined surface on stainless steel 304
1Photonik-Zentrum Kaiserslautern e.V., 67633 Kaiserslautern, Germany and Research Center OPTIMAS, TU Kaiserslautern, 67663 Kaiserslautern, Germany; 2Institute of Surface and Thin Film Analytics, IFOS, Research Center OPTIMAS, TU Kaiserslautern, 67663 Kaiserslautern, Germany; 3IVW—Institute for Composite Materials GmbH, Manufacturing Science, 67663 Kaiserslautern, Germany
Recently, controlling the wettability of metallic surfaces by laser micromachining has become important for many technical applications. However, there is still a challenge in understanding chemical effects on contact angle (CA) since there is even a big gap in knowledge of the laser micromachining’s influence on the surface chemistry. In this study, the relationship between the local surface chemistry at ps laser micromachined surfaces on stainless steel 304 and CA was discussed by using a new model description, based on a multiple regression analysis. The proposed model was verified by using experimental wetting behavior of different kinds of liquid and surface chemistry, characterized by XPS spectroscopy. To have a variety of different wettability of the samples, different structures, storage conditions, and post processes were tested. As a result, our proposed model showed a nice correlation between predicted CA from chemical components and measured CA.