On the Fabrication of Functionally Graded Prototypes with Laser Powder Bed Fusion from Reused Ni-625 and 17-4 PH Stainless Steel Powder
摘要
In the past decade, some studies have been reported on fabricating functionally graded prototypes (FGP) with laser powder bed fusion (LPBF). But hitherto, little has been reported on the reuse of LPBF fallow powders 17–4 precipitate-hardened (PH) stainless steel (SS) and Ni-625 for 3D printing of FGP to address issues related to implants such as stress shielding, wear, corrosion, porosity, and surface characteristics etc. in biomedical applications. This study reports the reuse of fallow Ni-625 and 17-4 PH SS powder on top and bottom layers with two different infill patterns (solid and octet) to ascertain the effect on wear, corrosion, and porosity of FGP to reduce stress shielding. The results suggest that for selected FGP, the ultimate tensile strength (UTS) was observed as 377 ± 4.5 MPa for solid infill and 290 ± 3.8 MPa for octet metastructure. The specific wear rate (SWR) was observed as 0.00036 mm3/Nm and 0.00041 mm3/Nm for solid infill and octet metastructure, respectively. The results also suggest that the porosity for Ni-625 was less than the 17-4 PH SS in 3D printed FGP for solid infill specimens. While comparing the solid and octet metastructure, octet infill resulted in a high porosity. The corrosion rate (CR) was observed as 1.069 × 10−8 mm/year and 2.027 × 10−8 mm/year for solid infill and octet metastructure. The results are supported by optical photomicrographs based on scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The simulation of temperature-dependent phase volume fraction changes in Ni-625 and 17-4 PH SS was also performed to understand various stable/metastable phases present in FGP. Finally, based on stress shielding, wear, corrosion, and porosity required for implants, octet infill is recommended to fabricate FGP with the LPBF.