PSI - Issue 54

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Daniel F.O. Braga et al. / Procedia Structural Integrity 54 (2024) 568–574 Daniel F.O. Braga et al. / Structural Integrity Procedia 00 (2023) 000–000

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Fig. 2. Cross-section of interface of DIN 1.2709 tool steel (SLM) and TS700 tool steel (LMD)

hybrid specimens are similar to other direct energy deposition tool steels, such as H13, Son et al. (2023) or 18Ni300, Yao et al. (2018). All specimens failed in a brittle manner, with fracture along a 45 º angle along the specimen width, starting from the interface between both materials and cracking through the SLM DIN 1.2709 tool steel.

Fig. 3. Example of Stress vs Strain curve of Run Order #1 of DIN 1.2709 tool steel (SLM) and TS700 tool steel (LMD)

The resulting Ultimate Tensile Strength (UTS) average and standard deviations are plotted in Fig. 4. It can be observed that some parameter combinations resulted in significant variations from the average UTS of all tested combinations. For example Run Order #7, which is a star point of the CCD, and as such with very low laser power (790 W) combined with median Scan Velocity and Powder Feed (900 mm/min and 10 g/min, respectively), resulted in a significant drop in UTS, while the center points of CCD resulted in significantly higher strength. This may indicate that the width of the parameter set chosen for the DoE may have been too wide, which will impact the accuracy of resulting model. Having manufactured and tested all parameter sets defined in the DoE, the average UTS for each run order was used in an analysis of variance (ANOVA), to determine the contribution of each process parameter and their combinations towards the strength of the combined hybrid SLM-LMD. A confidence level of 95 % was used.