# Fabrication of Smart Materials Using Laser Processing: Analysis and Prospects
## 3 Harnessing Photothermal Reactions and Functional Additive Introduction
Alloying, for instance, involves introducing elements or alloys to enhance a wide range of material properties, such as strength, hardness, and corrosion  
Figure 5: Laser cladding process employed to produce the multilayer Ca/P bio-ceramic coating [100]. resistance. Cladding, on the other hand, revolves around the application of a layer of one material onto the surface of another, thereby modifying its characteristics [52; 101; 102]. It is worth noting that the improper selection of cladding process parameters and the mismatch of thermophysical properties between the cladded layer and the substrate material can lead to the development of substantial residual stresses during rapid cooling and heating phases, potentially resulting in various types of cracks [103]. In [104], NiCrSiBC-WC composite coatings were studied with different WC mass ratios on carbon steel substrates, revealing that 40 wt.% WC coatings were crack-free, while those with 50% and 60% WC displayed cracks (Figure 6a). The integrated control system used at the workstation was finely tuned with specific processing parameters: a laser power of 1 kW, a laser spot diameter of 2.5 mm, a laser scanning speed set at 1200 mm/min, and an overlapping rate fixed at 40%. Figure 6b displays metallographic microscopy images of cladding coatings with different WC types in Ni60 coatings: spherical, shaped, and flocculent [105]. The processing was conducted using a semiconductor laser and a five-axis numerical control system. Composite powders were conveyed using coaxial-powder feeding technology. The processing parameters for the cladding layer were specified as follows: a laser power of 1.5 kW, a laser scanning speed of 240 mm/min, a powder feeding rate of 7 r/min, a spot size measuring 4 \(\times\) 5 mm, with an overlapping rate set at 40%. It was determined that under the same laser cladding process conditions, the addition of different WC particles has a different effect on the performance of Ni60-30 wt.% WC coatings. To produce top-quality laser cladding coatings, the interplay between processing parameters, microstructure, and mechanical properties is thoroughly examined in [106]. In addition, the study in [107] proposed optimizing the laser cladding process parameters through intelligent system optimization algorithms. Cladding can also be achieved through the use of transition layers [108], and the process itself can lead to the creation of functionally graded materials [109] and refractory high-entropy alloys with distinct microstructures and properties [110; 111]. The application of laser cladding for the fabrication of high-entropy alloys is thoughtfully presented in [112; 113]. This approach, which introduces functional additives into materials using laser processing, contributes to the creation of smart materials with tailored and enhanced properties, promising a wide array of applications. Doping, on the other hand, involves the introduction of specific elements, known as dopants, into the crystalline structure of a material. This process is carried out to modify the material's electronic properties, encompassing conductivity and optical characteristics [114]. Laser processing comes into play when introducing nanoparticles or creating nanostructures to enhance a material's conductivity, optical attributes, or other relevant  
Figure 6: Influence of cladding materials on the microscopic morphology of the coating. (**a**) Microstructure of NiCrBi-WC coatings with variable WC contents [104]; (**b**) microscopic images of different WC-based coatings in Ni60-30 wt.% WC composite coatings [105]. characteristics. Moreover, introducing functional additives onto a material's surface using laser processing can lead to changes in its adhesion, wettability, or chemical reactivity. Integrating functional elements like quantum dots or fluorophores using laser processing can result in the development of sensors and detectors with tailored functionality [115].