## 3 LMD of Ti6 Al4V
### Process Parameters
\begin{table}
\begin{tabular}{l c c c c c c} \hline \hline  & **Powder** & **Laser** & **Scanning** & **Laser Spot** & **Geometry** & **Powder Type/** \\  & **Feeding Rate** & **Power** & **Speed** & **Diameter** & **of Samples** & **Particle Size** \\  & **\(m_{P}\) (kg/h)** & **\(P_{L}\) (W)** & **v (mm/min)** & **d (mm)** & **(mm)** & **\(d_{P}\) (\(\mu\)m)** \\ \hline Kelbassa [20] & 0.036–0.096 & 250–500 & 500 & 1.3 & \(50\times 10\times 10\) & GA/45–71 \\ Mahamood & 0.12–0.24 & 1500–3000 & 3000 & 3 & 6 layers & GA/150–200 \\
[21; 22; 23; 24] & 0.12–0.24 & 1500–3000 & 3000 & 3 & 6 layers & GA/150–200 \\ [PERSON] [25] & – & 600–1800 & 300 & 4 & Single tracks & \(-\)/150–200 \\ [PERSON] [26] & 0.18 & 410–415 & 510 & 3 & \(38.1\times 12.7\times 3\) & \(-\)/44–149 \\ [PERSON] [27] & – & 3500 & 120–2400 & 0.5–4.1 & \(250\times 250\times 400\) & \(-\)/10–200 \\ [PERSON] [28] & 0.9–1.8 & 7000 & 600–900 & 6 & \(80\times 53\times 60\) & \(-\)/40–100 \\ [PERSON] [29] & 0.36–0.96 & 800–1500 & 600–1000 & 0.2–6 & Thin walls & \(-\)/75–105 \\ [PERSON] [30] & 0.48 & 2000 & 636 & 4 & Thin walls & PREP/89 \\ [PERSON] [31] & 0.576 & 350 & 1015.8 & 1.1 & 5 layers & PREP/45–150 \\ [PERSON] [32] & 0.1 & 2000 & 400 & 1.4 & \(39\times 20\times 5\) & PREP/45–78 \\  & 0.019 & 300 & 600 & 0.036 & & \\ [PERSON] [33] & 0.36–3.54 & 6000 & 1000 & 6 & Thin walls & PREP/80–250 \\ [PERSON] [34] & 0.18 & 500 & 634.8 & 1.24 & \(24\times 38\times 9\) & \(-\)/126.8 \\ [PERSON] [35] & 0.24 & 1500 & 500–700 & 2 & \(20\times 4.5\times 2\) & GA/45–100 \\ [PERSON] [36] & – & 480–1800 & 700–1000 & – & \(22\times 22\times 16\) & PREP/45–150 \\ [PERSON] [37] & – & 550–750 & 200–400 & 3 & \(12.7\times 6.4\times 50.8\) & \(-\)/106–175 \\ [PERSON] [38] & 0.432 & 710–940 & 600 & 1.83 & \(40\times 40\times 40\) & \(-\)/45–150 \\ [PERSON] [39] & 0.06/0.12 & 330/780 & 600/800 & – & \(102\times 51\times 8\) & GA/\(-\) \\  & & & & & & \(64\times 13\times 43\) \\  & & & & & & \(51\times 13\times 38\) \\ [PERSON] [40] & 0.126 & 400 & 635 & – & 4 layers & PREP/44–120 \\ [PERSON] [41] & 0.042–0.18 & 600 & 762 & – & Thin walls & \(-\)/44–177 \\ [PERSON] [42] & 0.72 & 2000 & 600 & 4 & Thin walls & PREP/58–156 \\ [PERSON] [43] & 0.468 & 350 & 1014 & 2.9 & \(6.6\times 6.6\times 78.2\) & PREP/45–150 \\ [PERSON] [44] & 0.4 & 800–2400 & 1000 & 4 & Single tracks & \(-\)/45–90 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Process windows of laser metal deposition (LMD) of Ti6 Al4V. Many researches are focused on effects of main process parameters on surface roughness, microstructures, deposition efficiency, corrosion resistance and wear resistance. The effects of these parameters can be summarized as follows:  
* Powder flow rate: an increase in powder flow rate can lead to an increase in microhardness and surface roughness [23]. * Laser power: A lower surface roughness can be achieved by using a higher laser power [24]; the porosity is inversely proportional to the laser power [25; 44]. However, with increased laser power, the corrosion rate and the microhardness are reduced [21; 47]. Laser power has significant effects on deposition efficiency and wear resistance as well; and strong interactions with scanning speed and the powder flow rate [4; 22]. Moreover, laser power shows a significant influence on the grain size and the phase structure--increased laser power leading generally to coarser grains and microstructures [36; 48]. * Scanning speed: an increase in scanning speed causes generally an increase in solidification rate, microhardness and surface roughness [21; 23]. [PERSON] has, in his work, observed that the wear resistance performance of samples rises first and then decreases with increasing scanning speed, with the turning point at 0.065 m/s [23; 49].