## 4 Conclusions  
Tests on the functional properties of surface layers produced using a laser clearly demonstrate an increase in the hardness and abrasion resistance of the obtained surface layer with the addition of chromium and nickel metal powders. With the addition of metallic powders, the silver surface layer has the form of a quasi-composite coating, consisting of elements present in the introduced metallic powders. The powders are present in the shape of particles visible on a scanning microscope and in the dissolved state in the matrix, as confirmed by the investigation into the chemical composition. In the case of surface layers produced after alloying with powders of a 1:2 mixture (Ni-to-Cr ratio), light and electron microscopy analyses confirmed the presence of a remelted zone with the occurrence of Cr particles introduced into the silver matrix in the upper and lower zones of the surface layer. It can be concluded that feeding the silver substrate with Cr and Ni metal powders achieved a good-quality surface, without cracks and defects, and with a hardness remarkably higher than that of the parental material. The hardness value increased with the used laser power; the highest power applied produced the highest hardness of the achieved remelted layer. Moreover, increasing the laser power increased the depth of the remelted surface layer; with increasing laser power, the surface became more regular and flatter with a visible smoothness. For the occurrence of the added metals, chromium and nickel were confirmed via EDS chemical microanalysis using a scanning and light microscope, where zones in the structure were also discovered. Three zones were discovered: the remelted zone (RZ), the heat-affected zone (HAZ), and the transition zone in between. On the basis of DSC analysis, it was found that the addition of Cr and Ni decreased the remelting temperature of the silver matrix by approximately 6.5%. The DSC curve during the heating of the alloy reached the endothermal area connected with the melting of the eutectic at 381 \({}^{\circ}\)C. This is evidence of the presence of additional phases, which are the components of a eutectic. The determined thermal effect of the melting reaction was equal to approximately +8.69 J g\({}^{-1}\). This is an important potential achievement of this study which could help minimize the cost of surface treatment based on traditional methods, such as heat treatment or plastic deformation. Instead of these methods, laser techniques can be used combined with the enrichment of the surface layer with additions of strengthening factors such as Cr- and/or Ni-phase particles, which do not participate in the solution process due to their low solubility and the short time of laser remelting. The hardness value increases with an increase in the laser power applied, so the highest applied power produces the highest hardness value in the melted layer, as in the tested case of 3.0 kW. As the laser power increased, the achieved depth of the surface also increased both the remelted zone and the heat-affected zone. Unfortunately, increasing the laser power also lead to an excessive increase in the roughness and depth of remelting, without a significant impact on the distribution of Ni and Cr particles in the Ag matrix. From the results of this study, the following can be concluded:  
1. It is possible to feed the Ni/Cr powder into a silver alloy surface layer using this type of laser device, as well as this feeding technology. 2. It is possible to use laser power in the range of 2.0 to 3.0 kW; however, the optimal laser power is 3.0 kW because of the optimal microstructure refinement and Cr phase distribution. 3. The optimal laser head speed is 0.5 m/s. For lower speeds, the remelting is too strong, causing huge roughness, whereas with laser speeds that are too high, remelting does not occur at all because of the line energy being too low. 4. Adding chromium and nickel to the silver alloy causes an overcooling of the alloy.