PSI - Issue 71

Ravi Prakash et al. / Procedia Structural Integrity 71 (2025) 325–332

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depositing five layers are 138.5 °C for case-I, 67.4 °C for case-II, 307.4 °C for case-III, and 152.4 °C for case-IV. Hence, for high power and low deposition speed, the peak temperature is maximum among all cases. The combined effect of high laser power and slow scan velocity results in a high energy density (energy per unit area). This high energy density intensifies the localized heating of the material, causing the temperature to rise to its peak much faster and higher compared to other process parameter combinations. When the laser moves slowly, heat has less time to dissipate to the surrounding powder or substrate, leading to an accumulation of thermal energy. This heat accumulation contributes to a higher peak temperature compared to scenarios where the laser moves quickly (higher scan speed), allowing more time for heat dissipation (Nabavi et al., 2024). Fig. 5 shows the location selected for temperature monitoring, while Fig. 6 illustrates the temperature distribution at the bottom and top of the substrate during deposition. Heat at the bottom mid of the substrate, far from the laser zone, is mainly conducted through the material due to its higher thermal conductivity compared to the powder bed. The substrate progressively transfers the heat from the built portion downward, which acts as a heat sink, dispersing the heat through the substrate's bulk and onto the surrounding area. This results in a much lower temperature at the bottom mid of the substrate compared to the interface or the build part. The top of the interface between the substrate and build part is close to the laser, directly exposed to repeated heating as layers of powder melt and solidify. This results in higher peak temperatures compared to the bottom of the substrate.

Fig. 4. Illustration of temperature contours: the temperature contour during fifth-layer deposition and after completion of five-layer deposition for (a) case I, (b) case II, (c) case III,and (d) case IV

Fig. 5. Location selected for monitoring the temperature field (a) at bottom of the substrate, (b) at the interface of top of substrate and build part.