After an aeroengine runs for a certain period of time, a layer of carbonization/oxidation deposits inevitably appear on the surface of the material, which then affects the performance of the engine. As a green cleaning technology, laser cleaning technology provides a green and efficient method for cleaning this deposition layer. In this study, a nanosecond pulsed laser was used to clean the high-temperature carbonization/oxidation deposition layer on the surface of a GH3128 nickel-based superalloy. The bonding mode between the substrate and deposition layer was analyzed, and the effects of different laser energy densities on the surface morphology, surface roughness, and element distribution following cleaning were investigated. The laser ablation thresholds of the loose layer on the surface and the dense deposition layer chemically bonded with the substrate were determined. The laser cleaning mechanism of this type of deposition layer is thus preliminarily obtained, thereby providing a valuable reference for the efficient and high-quality cleaning of this type of deposition layer.

In this study, a laser confocal microscope was used to observe the microscopic and three-dimensional (3D) morphology of the deposition layer after cleaning and to measure the surface roughness. Scanning electron microscopy (SEM) was used to observe the microscopic morphology after laser cleaning at a high power, and X-ray diffraction (XRD) was employed to analyze the phase of the original deposition layer. An energy spectrum analyzer (EDS) was used to observe the element distribution and regional element content after cleaning and to assess the cleaning effect. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical composition of the surface after laser cleaning.

The deposition layer is divided into loose surface and dense deposition layers chemically combined with the substrate, as shown in Fig. 1(e). The main factor affecting the removal of the deposition layer is the energy density of the laser. When other factors remain unchanged, the cleaning threshold of the loose deposition layer is reached when the laser energy density is 0.89 J/cm², as shown in Fig. 3(c). After cleaning, the surface of the material does not melt, and the loose deposition layer is removed. When the laser energy density is 1.07 J/cm², the threshold for the formation of the mixed melt of the material is reached, as shown in Fig. 4(c). Here, the melting phenomenon after cleaning can be clearly observed. Detection by EDS and XPS reveals that the deposition layer has not been fully removed. The study shows that the mixed melt is formed at this energy density. The laser energy density continues to increase. When the laser energy density reaches 2.85 J/cm², the mixed melt of the material is removed by EDS and XPS detection after cleaning, and the remaining contents of C (mass fraction of 2.7%) and O (mass fraction of 1.1%) are the lowest. Compared with the original deposition layer showing a decrease of 83.4% and 96.4%, respectively, the cleaning effect is the best.

The high-temperature carbonization/oxidation deposition layer on the surface of the GH3128 superalloy can be divided into loose surface and dense deposition layers chemically combined with the matrix. When the laser energy density is 0.89 J/cm², the laser cleaning threshold of the loose deposition layer is reached, and when it is 1.07 J/cm², the mixed melt is formed by dense deposition layer and the original oxide layer. When the laser energy density is 2.85 J/cm², the laser cleaning threshold of the mixed melt formed by the dense deposition layer and the original oxide layer is reached. Following cleaning, the contents of C (mass fraction of 2.7%) and O (mass fraction of 1.1%) on the surface of the material are the lowest, and those of C (mass fraction of 2.7%) and O (mass fraction of 1.1%) on the surface of the material are reduced by 83.4% and 96.4%, respectively, as compared with those of the original deposition layer. Vibration stripping and thermal ablation are determined to be the main laser cleaning mechanisms of the high-temperature carbonization/oxidation deposition layer on the surface of GH3128.