Excimer laser cleaning of black sulphur encrustation from silver surface

Abstract

The process of localized cleaning of silver sulphide from the silver surface has been investigated in this work. An artificial black encrustation was generated on the silver surface and its laser cleaning was performed using an excimer laser (KrF based) working at a wavelength of 248 nm and pulse width 25 ns. Laser process parameters i.e. laser fluence and number of pulses were used to perform the experiment and after different optical, microstructural, elemental, microhardness and surface topography analysis of the laser ablated zone was performed. The parametric window selected for the excimer laser cleaning were laser fluence (200-400 mJ/cm 2 ), repetition rate 4 Hz and number of pulses (60-300). It was observed that excimer laser is very effective in the cleaning of black encrustation having ~ 6 wt. % of sulphur from the surface without any significant removal of the silver substrate. The fluence value of 260.48 mJ/cm 2 was observed as above threshold value for removal of sulphide from the encrusted surface while a fluence of 384.85 mJ/cm 2 and 220 pulses showed the maximum removal of sulphur encrustation (~0.38 wt. % of sulphur remaining). Formation of the peripheral rim was observed to occur above 280.17 mJ/cm 2 of fluence value. The topography of the ablated surface showed a removal of 5-10 µm of the sulphide layer from the surface whereas the thickness of the sulphide coating was around 8-10 µm. Microhardness value showed a change of microhardness of the silver surface from 75.12 HV 0.5 (uncoated parent silver) to 96.07 HV 0.5 (centre of the ablated zone).Finally, it was concluded that excimer laser cleaning is a novel method for localized removal of silver sulphide encrustation from silver surface.

Effects of Different Post-Treatments on Arc Erosion Resistance of Cold-Sprayed AgC Composite Electric Contact

“…It was obvious that the Ag particles had experienced large plastic deformation resulting from high-speed collision with the substrate and formed irregular island-like shapes (Figure 5a). After surface laser treatment with a scanning speed of 4000 mm/min, a rough surface morphology with complex structures and particles ( Figure 5b) was observed due to the melting caused by the pulsed laser [18,21]. As shown in Figure 5c, the surface of the coating after annealing for 2 h at 400 °C exhibited a relatively smooth and flat surface since the recrystallization of Ag grains [15].…”

Imaging Feature Analysis-Based Intelligent Laser Cleaning Using Metal Color Difference and Dynamic Weight Dispatch Corrosion Texture

“…Feature Name Feature Dimension 1 Laser power, linear velocity, and line spacing 3 2 Energy, entropy, contrast, and correlation of GLCM in four directions 1 16 3 Concave-convex feature of image 1 1 The directions of 0 In general, two methods are utilized to tune the SVM parameters, including the manual adjustment method and the intelligent optimization algorithm. The manual parameter adjustment method uses the research experience of humans to control the parameters, while the intelligent optimization algorithm can realize automatic parameter setting.…”

“…Laser cleaning is a green and environmentally friendly technology that has been widely used in the preservation of cultural heritage, nuclear fusion research, ship repair and industrial manufacturing [1][2][3][4][5]. Laser cleaning has many advantages, including good cleaning quality, high cleaning efficiency, and stable cleaning precision.…”

Mel-frequency cepstral and spectral flux analysis of the acoustic signal for real-time status monitoring of laser cleaning

“…Accordingly, numerous studies had been conducted to determine how laser technology could be used to effectively decontaminate metallic or nonmetallic surfaces [1,2]. Despite a focus on process optimization, the need for a monitoring system for laser cleaning is undeniable, as it has also been demonstrated to be essential for attaining the desired cleaning quality [3,4].…”