Investigation of micron-sized fish-scale surface structures on tool steel surfaces using laser galvanometer scanning

Abstract Micronized structured surface exhibits excellent surface functions for surface science applications. However, the cost is high for fabricating, especially specialized structure surfaces. The work prepared the micron-sized fish-scale surface structures on rough DC 53 tool steel surfaces. CW (continuous wave) laser beam irradiation method was used from a scanning galvanometer in the filling scan mode. The surface morphology and structure before and after laser irradiation were analyzed by optical microscopy, laser scanning confocal microscopy, and scanning electron microscopy. The elemental distribution of the structure was measured by energy dispersive spectroscopy (EDS) and Auger electron spectroscopy (AES), with the chemical analyses detected by the X-ray photoelectron spectroscopy (XPS). The combination of the AES with XPS analysis was also developed by the ion sputtering with the depth etching. It is found that the fish-scale surface structures can be prepared using a crossover laser scanning method, and their formation is based on superficial surface melting achieved by laser irradiation. The XPS results showed that the oxide layer of the fish-scale surface was composed of FeO, Fe2O3 and SiO2. The AES and EDS results showed the high content of Si and O in the fish-scale surface structure boundary. The combination of AES and XPS results showed that the boundary of the fish scale was composed of SiO2. Laser fluence and scanning mode were the key factors in the preparation of micron-sized fish-scale surface structure. A laser fluence of 33.16 J/mm2 induced a well-defined fish-scale corrugated structure. At the scanning speed of 140 mm/s, the flow of material on the surface of the tool steel was gradually controlled, and the shape of the fish-scale structure tended to be obvious. The scanning method has a significant effect on the spacing of the fish scales on the surface. By adjusting the appropriate scanning pitch, a regular distribution of the fish scale surface structure can be obtained. It is indicated that the precipitation of SiO2 (inclusions) has a great potential for the structuring of the fish-scale surface on DC 53 tool steel.