## 4 Discussion  
In this study, the degrees of elongation of the M100 samples significantly exceed those of the M290 samples in the as-built and heated states; therefore, the null hypothesis was rejected. The main differences between the EOS M100 and M290 machines are as follows: the M100 uses a fiber laser with a power of 200 W and a diameter of 40 \(\upmu\)m, whereas the M290 employs a fiber laser with a power of 400 W and a diameter of 100 \(\upmu\)m. Consequently, the M290 exhibits higher output power and a larger laser track, leading to the formation of coarser grains. In contrast, the grains in the samples prepared using the M100 are finer due to its narrower laser track and lower laser power. These finer grains in the M100 samples contribute to their higher degrees of elongation in both the as-built and heated states [28,29]. The tendency of precipitates in M100 and M290 did not show significant differences. Therefore, it can be said that the influence of precipitates on ductility is minimal. XRD results showed that in as-built states, M290 samples have a stronger [200]-texture compared to the M110 samples. Thus, M290 samples can have stronger anisotropy. However, after heat treatments, both samples did not exhibit [200]-texture; thus, it is anticipated that both samples are homogenized, and the influence of anisotropy will be almost negligible in both M100 and M290 samples after heat treatment. The presence of internal porosity in Co-Cr alloys fabricated using SLM is a critical concern for biomedical materials, as it can reduce mechanical properties and increase susceptibility to corrosion. The density of the fabricated samples is influenced by process parameters such as laser power, scanning speed, layer thickness, and scanning pitch, and optimal parameters can achieve a density of over 97% [30]. Additionally, the scan strategy significantly affects the density of metal samples fabricated by the SLM process. The chessboard scan strategy rotated by 45\({}^{\circ}\) every layer decreases the internal porosity of Co-Cr alloy up to 0.1% [31]. The strategy of rotating the irradiation by 67\({}^{\circ}\) for each layer effectively eliminates pores formed in the lower layers, creating a high-density Mg alloy (close to 99%) [32]. In this study, internal porosity was not detected in the samples even under examination using an optical microscope, which suggests fully dense samples were obtained. This is attributed to the  
Figure 10: Stress-strain curves of the representative Co–Cr–Mo alloy samples. specimen preparation conditions applying the optimized parameters recommended by the manufacturer with a 67\({}^{\circ}\) rotation scan strategy. However, it has been reported that even a small amount of internal porosity was observed in metal frameworks for removable partial dentures with complex geometry fabricated by SLM [33]. This suggests that complete control of internal porosity may be challenging and warrants careful attention for clinical application. Following heating, we observed a significant reduction in the 0.2% PS, a decrease in the UTS, and an increase in elongation, accompanied by a drastic increase in the rate of twins (\(\Sigma\)3 boundaries). This indicates that recrystallization occurs with the M100 as well as the M290 [3]. However, the recrystallization of the M100 samples is faster than that of the M290 samples, as high KAM values are still observed for several grains of the heated M290 samples. The KAM values indicate the differences in crystal orientations of adjacent measurement points and are typically used to evaluate residual plastic strains and dislocation density [34; 35; 36]. Recrystallization is traditionally defined as a phenomenon in which the internal energy accumulated due to plastic deformation is released, and new crystal grains are formed when metallic materials are heated to high temperatures. The energy required for this process primarily consists of the stored dislocation energy from plastic deformation.