## 2 Materials and Methods
### Methodology
#### 2.2.4 Polishing  
Macro-polishing: Based on the previous study conducted by [PERSON] et al. [49] while investigating the effect of shallow surface melting and surface over-melting during laser polishing, the process can be classified into two main categories, termed macro-polishing and micro-polishing. The difference between these two categories is primarily defined by the depth of the molten layer, which could be either \"deep\" or \"shallow\" with respect to the height of the asperities. The macro-polishing process can be used to polish the surface roughly, while micro-polishing can smooth the roughly polished surface. For the macro-polishing process in this study, the CW laser was used. During the polishing process, the CW laser power was varied from 1000 W to 1600 W with 200 W increments and the travel speed was varied from 300 to 750 mm/min. While the focal offset distance of the CW laser and scan pattern for the macro-polishing process remained identical to the deposition offset distance and scan pattern, unlike the scanning deposition direction, the surface was scanned along the Y-axis during macro-polishing. Table 4 represents different process parameters used for rough polishing the top surface of samples #13 to #28. Before the polishing process, the samples were deposited and machined with optimal process  
Figure 4: Schematic representation of the pulsed laser focal offset distance used for (**a**) machining and (**b**) micro-polishing.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline
**Sample No.** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** & **9** & **10** & **11** & **12** \\ \hline Travel speed (mm/min) & 150 & 150 & 150 & 225 & 225 & 225 & 300 & 300 & 300 & 375 & 375 & 375 \\ Number of cycles & 1 & 2 & 4 & 1 & 2 & 4 & 1 & 2 & 4 & 1 & 2 & 4 \\ Number of scan passes per mm & 72 & 144 & 288 & 48 & 96 & 192 & 36 & 72 & 144 & 29 & 58 & 116 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Design of experiments for the machining process of Scalmalloy samples #1 to #12.  
parameters obtained from the laser-aided machining process. After macro-polishing, the surface roughness of each sample was measured and the optimal process parameters for the macro-polishing process were derived by analyzing the results.  
Micro-polishing: After obtaining the optimized process parameters for the machining and macro-polishing processes, samples #29 to #44 were deposited, machined, and roughly polished with the resultant process parameters to prepare the samples for further polishing processes. An additional surface finishing process named micro-polishing was introduced in this study to fine finish the surface of the roughly finished part. The PL and scan pattern (shown in Figure 2b) implemented in the machining process were also used for the micro-polishing process. Compared to the machining process, the travel speed, laser power, and focal offset distance were varied. While the scanning speed was equal to the speed used for the machining process, during micro-polishing, the focal offset distance of the PL was set at 20 mm as shown in Figure 4b. The PL power was varied from 40 to 100 W with a 20 W increment and the travel speed was changed from 300 to 750 mm/min with 150 mm/min increments in each step. Table 5 represents different process parameters used for the micro-polishing process. After the final polishing process, the surface roughness of the samples was measured to obtain the optimal process parameters for the micro-polishing process. Figure 5a,b exhibit the surface texture of samples after the final polishing process.