Research on nanosecond laser processing of basic unit for ridge surface: forming condition of microgroove and micro-ridge structure on TC4 surface

Abstract

Frictional resistance significantly reduces the energy efficiency of aircraft. The ridge surface has a drag reduction effect, and its processing has become one of the important ways for improving the energy efficiency of aircraft. The micro-ridge and microgroove are the basic units of the ridge surface. A nanosecond laser can prepare them. However, numerous parameters and complex laser etching mechanisms make it difficult to determine their molding conditions, the forming quality of which is difficult to guarantee. This problem restricts the high-precision preparation of the ridge surface, which inevitably affects its drag reduction performance. Therefore, it is crucial to determine the high-quality molding conditions of the microgroove and micro-ridge to ensure the drag reduction effect of the ridge surface. Here, we focus on aviation titanium alloy TC4. Through an etching experiment of the straight section, the influence of parameters on the feature size of its cross-section profile is systematically studied. The recast layer scale, symmetry, and smoothness of the cross-section profile are used to evaluate the molding quality of microgrooves. The symmetry of the cross-section profile assesses the molding quality of micro-ridges. The forming parameter range and high-quality forming condition of microgrooves and the high-quality forming parameter range of micro-ridges are determined. Finally, the morphology evolution rule and mechanism of the nanosecond laser etching TC4 is revealed based on this research. The direct molding rules and parameter range of micro-ridges on the TC4 surface are reported and show a broadening of the nanosecond laser micromachining range. Moreover, this study will provide a process window for optimizing nanosecond laser processing for microgrooves and micro-ridges on the TC4 surface.