On Development and Characterization of Functionally Graded Material with Minor to Considerable Melting Temperature Variation Processed by Laser Powder Bed Fusion
摘要
In the past, significant studies have been reported on the design and development of functionally graded materials (FGM) with minor differences in melting temperature (~50-100 °C) using the laser powder bed fusion (LPBF) process. However, little has been reported on the design and development of FGM with a significant difference in melting temperature (~100-500 °C). This study reports the challenges in interlayer bonding of FGM by considering minor and significant differences in melting temperature. The 17-4 precipitate hardened (PH) stainless steel (SS) and Ni-625 alloys were processed in stage 1 with LPBF (having a minor melting difference of ~ 50 °C). In the next stage, Ti-6Al-4 V and Ni-625 were processed (with a considerable melting difference of ~ 450 °C). The study suggests that by controlling LPBF parameters, dimensional stability, surface, and morphological properties may be tuned for customized applications. The microhardness of 367 HV for 17-4 PH SS, 385 HV for Ni-625, and 273 HV for Ti-6Al-4 V was observed in LPBF-processed FGM. The results revealed FCC (austenite) as the dominant phase at Ni-625-17-4 PH SS interface along with intermetallics (Nb, Cr rich) and sigma phase (Cr, Mo and Fe rich). In the case of the Ni-625- Ti-6Al-4 V interface, BCC is the dominant phase, and the NiTi2 intermetallic and silicate phases were in small amounts. The results are also supported by melt pool analysis for heat gradients and solidification behavior.