Towards Improving Surface Hydrophobicity by Laser Texturing Steel Surfaces
Laser texturing of carbon steel surfaces is carried out under the high pressure N2 assist gas. The morphological and metallurgical changes in the laser treated layer are examined. The hydrophobic characteristics of the laser textured surfaces are assessed incorporating the water droplet contact angle measurement method. It is found that laser treated surfaces composes of micro/nano textures with the average surface roughness (Ra) in the order of 2.4 mm. The combination of evaporation and melting at the irradiated spot reduces the texture height and surface roughness. The presence of closely spaced laser scanning tracks generates self-annealing effect in the treated layer while modifying the thermal strain in this layer. Laser textured surface demonstrates hydrophobic characteristics and some small variation of water droplet contact angle is observed because of non-uniform texture distribution at the surface; nevertheless, this variation is small.
Keywords: CO2 laser, carbon steel, laser texturing, gas assisted process, surface roughness, wettability, hydrophobicity