## 3 Results and Discussion

Table 3: Quantitative EDS analysis of the AgCrNi surface after laser treatment for the areas marked in Figures 5 and 6.  
peak (510 \({}^{\circ}\)C) is related to nickel (Ni) as well as the transformation of chromium and the Cr phase in the Ag alloy during cooling. The main results obtained during the analysis of the DSC test also include a demonstration that the addition of Ni and Cr reduces the melting point of the tested silver alloy--after alloying--by approximately 6.5%. An overcooling of the alloy was observed, where the temperature difference of the first phase transformation during the cooling of the pure silver (430.70 \({}^{\circ}\)C) compared to the silver alloy with Cr and Ni addition after laser treatment (424.96 \({}^{\circ}\)C) reached 5.74 \({}^{\circ}\)C (1.3%). Figure 11 presents the measured hardness of the surface layer for a 3 kW laser power. The hardness of the remelled zone was significantly higher than that of the parental material. The average hardness of the obtained layer was about 92 HV0.3. The value of the Ag substrate was equal to 42 HV0.3 and increased slightly in HAZ to 46 HV0.3. It should also be noted that, based on the results of the preliminary tests, the measured hardness increased with the laser power, reaching the highest value at a 3.0 Kw laser power (Table 4). For this reason, only the results for the 3.0 Kw laser power are presented in this paper. Figure 10: DSC curve of the Ag-Ni-Cr material while cooling. Figure 9: DSC curve of the Ag-Ni-Cr material while heating. The applied laser surface treatment of the silver surface increased the hardness by over 100%, from 42 HV to 92 HV. This was due to the presence of hard chromium and nickel particles in the remelted surface layer, which had not dissolved in the Ag matrix but built a well-dispersed mesh of fine-graded particles. Figure 12 displays the depth and width of the laser traces, and reveals values of 2.4 and 2.6 mm measured for the depth and width of the produced trap, respectively. It is remarkable that the parameter reaches the value of zero for a 1.5 kW laser power. Generally, with an increase in the laser beam line energy, the depth of the remelted material increases according to the increase in the laser power, with clear visible differences in the roughness of the surface after laser treatment (Figure 13). \begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{3}{c}{**Hardness of the Remelting Zone, HV0.3**} \\ \hline
**2.0 kW** & **2.5 kW** & **3.0 kW** \\ \hline
79 & 82 & 92 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Hardness increased in the remelting zone according to the used laser power. Figure 11: Surface hardness of the treated Ag surface layer, HV0.3. It was found that, as the laser power used increased, the material melting depth increased. As the laser power increased, the remelted surface became smoother and flatter, without major surface defects. The presence of metal admixtures, such as the added chromium and nickel, could be confirmed in the obtained surface layer using EDS microanalysis. Metallographic examinations under scanning and light microscopes revealed a zone structure consisting of three zones. Three zones of the surface layer were found, i.e., the refusion zone (RZ), the heat-affected zone (HAZ), and a small transition zone, as well as the native material not affected by heat (Figure 14). The research performed and described in this article allowed for the implementation of research ideas, primarily determining the suitability of the application and use of laser surface treatment in order to improve the mechanical and operational properties of the surface of silver alloys, allowing for the creation of a surface layer characterized by better mechanical and tribological properties compared to the tested metal without surface heat treatment in the as-cast state. This is a very important achievement that could help minimize the cost of surface treatment based on traditional methods, such as heat treatment or plastic deformation.