On failure analysis of three-dimensional printed functionally graded material prepared by direct metal laser sintering

In the past decade, some studies were reported on the successful three-dimensional printing of meta-structure-inspired functionally graded material with two different alloys (having a wide difference in melting range ≈ 450–500 °C) by direct metal laser sintering. But hitherto little has been reported on failure analysis of such meta-structure-inspired three-dimensional printed functional prototypes of dual alloys (17-4 precipitate hardened (PH) stainless steel (SS) and Ti-6Al-4V) with direct metal laser sintering (while fabrication). This study reports the failure analysis of meta-structure inspired dual alloys printing (as FGM) at different processing parameters of direct metal laser sintering. Initially, a pilot study was performed in which a solid structure of Ti-6Al-4V and 17-4 PH SS was successfully printed by selecting the suitable direct metal laser sintering process parameters as functionally graded material (stage 0). In the next stage, specimens of dual alloys were printed with dodecahedron and octet meta-structure of Ti-6Al-4V as a sandwich between the 17-4 PH SS and Ti-6Al-4V layers (stage 1). It has been observed that the octet-based specimen was successfully printed, while the dodecahedron-based sample failed after attaining some height. After successfully octet meta-structure printing of dual alloys (Ti-6Al-4V and 17-4 PH SS), direct metal laser sintering process parameters were further explored for optimization (stage 2). For failure analysis, the specimens with octet meta-structure were fabricated by fixing energy density (in stage 3), hatching distance (in stage 4), laser power (in stage 5), and energy density, hatching distance, laser power, scanning speed (in stage 6). Finally, for confirmation (stage 7), a single specimen was successfully printed by taking process parameters of the successful octet-based sample of stage 2. All the printing failures as per porosity analysis (such as balling phenomenon, caves, and cervices formation) concerning the number of sintered layers in this study are supported with photomicrographic analysis (based on scanning electron microscopy images).