Abstract
Laser powder bed fusion (LPBF) of Zn-based metals exhibits prominent advantages to produce customized biodegradable implants. However, massive evaporation occurs during laser melting of Zn so that it becomes a critical issue to modulate laser energy input and gas shielding conditions to eliminate the negative effect of evaporation fume during the LPBF process. In this research, two numerical models were established to simulate the interaction between the scanning laser and Zn metal as well as the interaction between the shielding gas flow and the evaporation fume, respectively. The first model predicted the evaporation rate under different laser energy input by taking the effect of evaporation on the conservation of energy, momentum, and mass into consideration. With the evaporation rate as the input, the second model predicted the elimination effect of evaporation fume under different conditions of shielding gas flow by taking the effect of the gas circulation system including geometrical design and flow rate. In the case involving an adequate laser energy input and an optimized shielding gas flow, the evaporation fume was efficiently removed from the processing chamber during the LPBF process. Furthermore, the influence of evaporation on surface quality densification was discussed by comparing LPBF of pure Zn and a Titanium alloy. The established numerical analysis not only helps to find the adequate laser energy input and the optimized shielding gas flow for the LPBF of Zn based metal, but is also beneficial to understand the influence of evaporation on the LPBF process.
Highlights
Laser powder bed fusion (LPBF), referred to as selective laser melting (SLM), is an appropriate additive manufacturing method for fabricating metal bone implants of customized geometry, since it allows the precise melting of discrete fine metal powders layer upon layer under computer programming with high efficiency and high quality [1,2]
Figure shows the comparison of theshape penetration shape in and the Zn
The4comparison of the penetration in the Zn plates the plates cal- and the calculatedcontours temperature contours corresponding to theoflaser powers ofW
Summary
Introduction published maps and institutional affilLaser powder bed fusion (LPBF), referred to as selective laser melting (SLM), is an appropriate additive manufacturing method for fabricating metal bone implants of customized geometry, since it allows the precise melting of discrete fine metal powders layer upon layer under computer programming with high efficiency and high quality [1,2].Bones are capable to repair themselves, and on many occasions, bone implants are expected to degrade gradually and dissolve completely with the reconstruction of new bones [3,4].Zn plays a vital role in bone metabolism and has a moderate corrosion rate in the human body, which tends to match the bone healing rate, as compared to fast-degrading Mg or slowly degrading Fe [5,6]. Laser powder bed fusion (LPBF), referred to as selective laser melting (SLM), is an appropriate additive manufacturing method for fabricating metal bone implants of customized geometry, since it allows the precise melting of discrete fine metal powders layer upon layer under computer programming with high efficiency and high quality [1,2]. Bones are capable to repair themselves, and on many occasions, bone implants are expected to degrade gradually and dissolve completely with the reconstruction of new bones [3,4]. The strength of pure Zinc is not enough for load-bearing implants. Yang et al made a comprehensive study on the biodegradable application of Zn alloys, and both in-vitro and in-vivo results were quite promising regarding mechanical strength, biocompatibility, biodegradation, and osteogenesis [7].
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