# Additive Manufacturing of PH 13-8 Mo Family: A Review
## 4 Comparison of PBF-LB and DED-Arc of PH 13-8 Mo Family  
Researchers compared the effects of different AM methods (PBF-LB and DED-Arc) on the microstructure, properties, and post-processing procedure of the PH 13-8 Mo family.  
[PERSON] et al. [74] investigated the influence of different AM methods on the hardness and the microstructure of PH 13-8 Mo. It was clear that the differences between the cooling rate and composition of feedstock material resulted in a different primary solidification  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Material**} & **Ref.** & **Process** & **Condition** & **Building** & \begin{tabular}{c} **Ultimate** \\ **Tensile** \\ **Strength** \\ **(MPa)** \\ \end{tabular} & \begin{tabular}{c} **Yield** \\ **Strength** \\ **(MPa)** \\ \end{tabular} & \begin{tabular}{c} **Elongation** \\ **(\%)** \\ \end{tabular} & **Hardness** & **Cooling** \\ \hline \multirow{4}{*}{\begin{tabular}{c} PH 13-8 \\ Moz \\ Moz \\ Moz \\ \end{tabular} } & \multirow{4}{*}{\begin{tabular}{c} Moniru- \\ zaman \\ 672 mm/s \\ \end{tabular} } & \multirow{4}{*}{\begin{tabular}{c} AAC: \\ 135 A \\ 28.8 V \\ \end{tabular} } & As-Built & V & 1046 & 860 & 14 & 33.6 HRC & - \\  & & & AV: 28 V & A: 400 \({}^{\circ}\)C for 312 min & - & - & - & - & 41.1 HRC \\  & & & WFS: & A: 460 \({}^{\circ}\)C for 77 min & - & - & - & - & 41.1 HRC \\  & & & & & & & & & \\  & & & & & & & & & \\  & & & & & & & & & \\ \hline \multirow{4}{*}{\
\begin{tabular}{c} PH 13-8 \\ Moz \\ Moz \\ \end{tabular} } & \multirow{4}{*}{
\begin{tabular}{c} Ana: Aging, AAC: Average Arc Current, AV: Arc Voltage, H: Horizontal, ST: Solution Treatment, TS: Travel Speed, V: Vertical, WFS: Wire Feed Speed. \\ \end{tabular} } \\  & & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 5: _Cont._phase. Therefore, the resulting as-built microstructure was different for the DED-Arc/PH 13-8 Mo and PBF-LB/PH 13-8 Mo. The DED-Arc/PH 13-8 Mo had a martensitic matrix, \(\delta\)-ferrite, and retained austenite. On the other hand, the PBF-LB/PH 13-8 Mo consisted of a martensitic matrix and a very low amount of retained austenite. The as-built hardness value of the DED-Arc/PH 13-8 Mo was higher than the PBF-LB/PH 13-8 Mo due to the existence of \(\beta\)-NiAl nano-precipitates, which formed due to repeated thermal cycles during the DED-Arc process. It was also concluded that direct aging heat treatment (530 \({}^{\circ}\)C--3 h) was not applicable for the DED-Arc/PH 13-8 Mo (only 6% increase in hardness), whereas it was applicable for the PBF-LB/PH 13-8 Mo (46% increase in hardness) (Table 6). 8-ferrite was still in the microstructure, and undesirable phases such as Cr\({}_{23}\)C\({}_{6}\) particles and reverted austenite (7.2%) were formed during the aging of the DED-Arc sample.  
[PERSON] et al. [75] studied the direct aging heat treatment of the PH 13-8 Mo manufactured using DED-Arc and compared it with the PH 13-8 Mo manufactured using LBF-LB. It was shown that the as-built microstructures of PH 13-8 Mo processed by two different methods had differences, such as martensite lath size, due to experiencing different cooling rates. The materials also exhibited different kinetics of precipitation hardening. Therefore, two different heat treatment procedures for each manufacturing method were recommended. The recommended aging temperature was 550 \({}^{\circ}\)C, and the aging time was 115 min for the PBF-LB/PH 13-8 Mo, which improved the strength and decreased the ductility compared to the as-built condition. On the other hand, the recommended aging heat treatment (495 \({}^{\circ}\)C--45 min) was successful in improving both the strength and the ductility of the DED-Arc/PH 13-8 Mo. The reason for the improvement in the ductility was stated as the formation of \(\beta\)-NiAl clusters instead of \(\beta\)-NiAl precipitates in the material. The obtained tensile properties and hardness according to recommended heat treatments can be found in Table 6.