Contamination of 316L powder with Ti6Al4V during laser powder bed fusion

Abstract

Cross-contamination of powders in metal additive manufacturing (AM) is concerning because it can alter the resulting mechanical properties. Stainless steel (SS316L) and Ti6Al4V (Ti64) are top choices for biomedical devices and are often used in metal AM. In this study, the effect of cross-contamination of Ti64 powder, up to 2 wt.%, on SS316L is investigated using laser powder bed fusion (LPBF). The contaminated materials were subjected to mechanical testing, namely tension, compression, micro-Vickers hardness, rotating bending fatigue, X-ray diffraction, optical microscopy, and scanning electron microscopy. Electron back-scattered diffraction (EBSD) analysis showed a 90% grain-size reduction for 2%Ti64-SS316L. EBSD in conjunction with EDS and the XRD results confirmed the formation of the delta ferrite phase in the contaminated materials. Test results showed an increase in the strength, hardness, and fatigue life of the contaminated materials; however, ductility was reduced. The change was significant, particularly for SS316L-2% Ti64, for which a 25% increase in tensile yield strength from 456 to 568 MPa, and a 32% increase in hardness from 235 HV0.2 to 311 HV0.2 was observed; however, the elongation dropped from 28.6% to 14.8%. Compared to control (SS316L), the fatigue limit of 2% Ti64-SS316L increased from 382 to 420 MPa.