Journal Article

Optimization of SLM process parameters for Ti6Al4V medical implants

Youssef, Yehia, Ghazy, Mootaz, Elsayed, Mahmoud, Essa, Khamis

2019

Overview

Purpose Ti6Al4V alloy has received a great deal of attention in medical applications due to its biomechanical compatibility. However, the human bone stiffness is between 10 and 30 GPa while solid Ti6Al4V is several times stiffer, which would cause stress shielding with the surrounding bone, which can lead to implant and/or the surrounding bone’s failure. Design/methodology/approach In this work, the effect of selective laser melting (SLM) process parameters on the characteristics of Ti6Al4V samples, such as porosity level, surface roughness, elastic modulus and compressive strength (UCS), has been investigated using response surface method. The examined ranges of process parameters were 35-50 W for laser power, 100-400 mm/s for scan speed and 35-120 µm for hatch spacing. The process parameters have been optimized to obtain structures with properties very close to that in human bones. Findings The results showed that the porosity percentage of a SLM component could be increased by reducing the laser power and/or increasing the scan speed and hatch spacing. It was also shown that there was a reverse relationship between the porosity level and both the modulus of elasticity and UCS of the SLM part. In addition, the increased laser power was resulted into a substantial decrease of the surface roughness of SLM parts. Results from the optimization study revealed that the interaction between laser process parameters (i.e. laser power, laser speed, and the laser spacing) have the most significant influence on the mechanical properties of fabricated samples. The optimized values for the manufacturing of medical implants were 49 W, 400 mm/s and 99 µm for the laser power, laser speed and laser spacing, respectively. The corresponding porosity, surface roughness, modulus of elasticity and UCS were 23.62 per cent, 8.68 µm, 30 GPa and 522 MPa, respectively. Originality/value Previous investigations related to additive manufacturing of Ti alloys have focused on producing fully dense and high-integrity structures. There is a clear gap in literature regarding the simultaneous enhancement and adjustment of pore fraction, surface and mechanical properties of Ti6Al4V SLM components toward biomedical implants. This was the objective of the current study.

• Publisher: Emerald Publishing Limited,Emerald Group Publishing Limited
• Subject: Additive manufacturing / Biocompatibility / Biomechanics / Bones / Compressive strength / Design of experiments / Design optimization / Laser beam melting / Lasers / Mechanical properties / Medical research / Modulus of elasticity / Optimization / Porosity / Process parameters / Rapid prototyping / Research methodology / Response surface methodology / Statistical analysis / Stiffness / Stress concentration / Stress shielding / Surface roughness / Surgical implants / Titanium alloys / Titanium base alloys / Transplants & implants / Variance analysis