1 Introduction and the need for laser cleaning process
Most of the industrial cleaning is currently carried out using manual processes employing aggressive chemicals, including hydrofluoric acid. So these conventional chemical cleaning methods adopted in industries are labour-intensive. And we using it multiple staged manual processes (up to 15 steps). These are error-prone and can expose the operator to hazardous processes. Furthermore, there are some drawbacks, such as processing of waste residue, uneven removal, and environmental concerns.
An alternative technology is to use laser systems as replacement for conventional chemical cleaning methods. Previous research on this technology has demonstrated a 20-fold reduction in cleaning time for aerospace components. Also, the laser cleaning process offers advantages such as the possibility of remote control, high speed, dry cleaning and, importantly, more environmentally-friendly processing.
Laser cleaning is the removal of particles or the removal of hydrocarbon contaminants from a solid surface . Typical mechanisms of laser cleaning are evaporation/spallation/ablation/shockwave generation. Besides, the resulting mechanisms cause the removal of the contaminants without causing any damage to the substrate.
Within the area of laser cleaning, several working mechanisms and processing types have been propose by researchers. For example, mainly include dry laser cleaning, wet laser cleaning, angular laser cleaning, shock laser cleaning, and hydrodynamics-based laser cleaning. We can see a simple schematic of the laser cleaning in Fig. 7.1.
1.1 Dry Laser Cleaning
Dry laser cleaning is widely used in industry and researched in academia. It is generally base on a rapid thermal energy transfer between the incident laser beam and the substrate/contaminant. The resulting rapid thermal expansion of the components provides the force to remove the particles  (Fig. 7.2). But a common problem encounter in this technique is the progressive loss of cleaning efficacy as the products of the decomposition progressively build up and mask the surface to be clean.