## 2 Materials and Methods  
The ASTM-5140 steel was selected as the substrate in this study with the size of 40 mm \(\times\) 20 mm \(\times\) 10 mm, in the background of crankshaft restoration in industrial application; its elemental composition was shown in Table 1. The powder used in laser cladding process was the mixture of 316L stainless steel powder and SiC powder produced by Xiangcheng Yuteng Ceramic Product CO., LTD (Zhangzhou, China) with both particle sizes ranging from 48 to 106 \(\upmu\)m, which met the requirement for the equipment specifications. Table 1 also shows the elemental composition of the aforementioned two type of cladding powders. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Material**} & \multicolumn{8}{c}{**Element (wt. \%)**} \\ \cline{2-10}  & **C** & **Si** & **O** & **Ni** & **Cr** & **Nb** & **SiC** & **N** & **Fe** \\ \hline ASTM-5140 & 0.37–0.44 & 0.17–0.37 & - & \(\leq\)0.30 & 0.80–1.10 & - & - & - & Rest \\
316L & 0.03 & 1 & 0.1 & 10–14 & 16–18 & - & - & 0.1 & Rest \\ SiC & - & - & - & - & - & 0.05 & Rest & - & 0.02 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Elemental composition (wt. %) of W6 Mo5 Cr4V2 high-speed steel powder. The laser cladding system used in this study was schematically illustrated in Figure 1. Four sub-systems build up the whole system, consisting control system, laser system, chamber system, powder and gas delivery system. The whole system was operated under the PLC control system made by Mitsubishi, Japan. The laser system included YLS-3000 laser generator and SX14-012 PUISE laser pulse control produced by IPG Photonics (Burbach, Germany). The generated laser energy was transmitted into the FDH0273 laser cladding nozzle with 300 mm focal length (Lasermech, Novi, MI, USA) to complete the laser cladding process in the chamber system, where the M-710 iC/50 industrial robot (FANUC, Yamanashi, Japan) and the TFLW-4000 WDR-01-3385 water cooling system (Sanhe Tongfei, Sanhe, China) were equipped. Argon gas was utilized as the carrier and protective gas by the CR-PGF-D-2 powder and gas delivery system (Songxing, Fuzhou, China) during the cladding process. Before the laser cladding process, the surface of ASTM-5140 steel substrate was cleaned with acetone. In the preparation of the laser cladding powder mixture, the 316L stainless steel powder and SiC powder were mixed in a MITR-YXQM-2L ball mill at a 400 rpm speed for 30 min, and then dried in a vacuum dryer at 80 \({}^{\circ}\)C for another 30 min afterwards [24; 25]. This study utilized an orthogonal array with five factors and four levels, with one factor as blank. The other four factors were the four processing parameters to be investigated in this study, as shown in Table 2. A full factorial experimental design would require 4\({}^{4}\) = 256 runs to include all the combinations in the four factors and four levels design. The Taguchi orthogonal design is a method of designing the experiment, which reduces the number of runs versus the full factorial design and obtains the optimal combination through orthogonal matrix [26; 27]. Thus, a L\({}_{16}\) (4\({}^{4}\)) Taguchi orthogonal design was developed with 16 runs, as shown in Table 3.  
Figure 1: Laser cladding system schematic illustration. The laser cladding process was conducted following the setup in Table 3, one sample was obtained for each run. After the completion, the 16 samples were prepared by linear cutting, grinding, and aqua regia immersing for measurement and testing in latter steps. After the sample preparation, the micro-hardness was tested by a 402 TS micro-hardness tester (HDNS, Shanghai, China) with applying 500 g force for 30-s duration. The measurement location was at the subsurface of the clad to guarantee the accuracy, since the incomplete melted material on top surface of the clad, while the bottom layer of the clad was diffused by the Cr and C element from the substrate. The wear resistance was interpreted by the indicator of wear volume.