# Additive Manufacturing of PH 13-8 Mo Family: A Review
## 2 PBF-LB of PH 13-8 Mo Family
### Material Properties  
#### 2.3.1 Tensile Properties and Hardness  
Table 3 shows the collection of tensile properties and hardness measurements for as-built and heat-treated PH 13-8 Mo processed using PBF-LB from the literature. [PERSON] et al. [42] published the first paper about the mechanical properties of CX using PBF-LB. The ultimate tensile strength (UTS = 1113 MPa) of the horizontally manufactured CX using PBF-LB was higher compared to the PBF-LB of other stainless steels (PH 17-4 and 316L) and compared to the CX data values from the manufacturer. The hardness of the as-built CX was 35 \(\pm\) 1 HRC. The influence of the built direction on the tensile properties and hardness of the as-built PBF-LB/CX was unfolded by [PERSON] et al. [53; 54]. It was observed that the different built orientations caused different thermal histories, which led to different hardness values. The vertically built sample had lower hardness compared to the horizontal sample due to the slower cooling rate, which resulted in in situ tempering. In addition, the vertical sample had lower UTS and elongation (1085 MPa--5.7%) than the horizontal sample (1092 MPa--21.2%), which was attributed to a higher austenite content, with higher hardening capacity due to transformation-induced plasticity (TRIP) effect in the horizontally built sample. [PERSON] et al. [55; 60] investigated the influence of the built orientation properties not only for as-built PBF-LB/CX but also for aged PBF-LB/CX. The elongation values of the vertical samples were lower compared to horizontal ones for the as-built and heat-treated conditions. This could be due to the lower austenite content of the vertical samples. On the other hand, the hardness, surface quality, and notch toughness were not significantly influenced by the building orientation. [PERSON] et al. [56] explored the influence of the heat treatment and the built direction on the tensile properties of the PBF-LB/Corrax. The fracture mode (ductile) of the samples was not really affected by the building direction or the heat treatment. Heat-treated vertical samples had lower elongations than horizontal ones because of their higher grain size. It is known that a finer grain size increases crack resistance and enhances elongation. [PERSON] et al. [51] studied the influence of the linear energy density on the properties of the as-built PBF-LB/CX, and 245 J/m was the value that resulted in the highest UTS (1068 \(\pm\) 5.9 MPa), total elongation (15.7 \(\pm\) 0.26%), and hardness (351 \(\pm\) 4.8 HV0.05). [PERSON] et al. [46] chose 63.97 J mm\({}^{-3}\) as the optimum process parameter, which resulted in the highest mechanical properties such as UTS (1084 \(\pm\) 3 MPa), yield strength (946 \(\pm\) 7.3 MPa), total elongation (17.64 \(\pm\) 0.18%), and hardness (374.2 \(\pm\) 6.5 HV0.05). The optimal tensile specimens showed dimples and necking, which represents ductile fracture. Strengthening mechanisms of PBF-LB/CX and Corrax in as-built conditions were also investigated by [PERSON] et al. [51] and [PERSON] et al. [46]. According to [PERSON] et al. [51], dislocation hardening (274.37 MPa) was found to be the dominant contributor to the yield strength, which was followed by grain boundary (236.50 MPa), texture (205.72 MPa), and precipitation hardening (164.53 MPa). In addition, the calculated and experimental yield strength were comparable. [PERSON] et al. [46] and [PERSON] et al. [51] confirmed that dislocation hardening has a significant role in strengthening, which is followed by grain boundary strengthening and precipitation hardening. The strengthening mechanisms of aged PBF-LB/CX were explored by [PERSON] et al. [48]. It was revealed that the yield strength of the aged PBF-LB/CX is provided by three different strengthening mechanisms such as sub-boundary (247 MPa), dislocation (679 MPa), and precipitation (602 MPa) hardening. The influence of three different heat treatments on the properties of PBF-LB/CX was investigated by [PERSON] et al. [47].