Abstract
One of the main challenges in additive manufacturing (AM) of medical implants for the treatment of bone tissue defects is to optimise the mechanical and biological performance. The use of post-processing can be a necessity to improve the physical properties of customised AM processed implants. In this study, Ti-6Al-4V coupons were manufactured using selective laser melting (SLM) in two build orientations (vertical and horizontal) and subsequently post-processed using combinations of hot isostatic pressing (HIP), sandblasting (SB), polishing (PL) and chemical etching (CE). The effect of the different post-manufacturing strategies on the tensile and fatigue performance of the SLMed parts was investigated and rationalised by observing the surface topography. Vertically built samples showed higher yield strength (YS) and ultimate tensile strength (UTS) than the horizontal samples, increasing from 760.9 ± 22.3 MPa and 961.3 ± 50.2 MPa in the horizontal condition to 820.09 ± 16.5 MPa and 1006.7 ± 6.3 MPa in the vertical condition, respectively. After the HIP treatment, the ductility was substantially improved in both orientations; by 2.1 and 2.9 folds in the vertical and horizontal orientations, respectively. The vertically built samples demonstrated a superior ductility of 22% following HIP and polishing. Furthermore, chemical etching was found to be the most effective surface post-processing treatment to improve the fatigue performance after HIP, achieving the highest run-out strength of 450 MPa. Most importantly, chemical etching after HIP enhanced the cellular affinity of the surface, in addition to its good fatigue performance, making it a promising post-processing approach for bone implants where tissue integration is needed.
Highlights
The development of additive manufacturing (AM) techniques has recently gained significant attention for the fabrication of customised implants to the needs of individual patients in healthcare [1,2].This strategy relies on 3D printing of the part from digital models in a layer-by-layer fashion in an attempt to add new implant functionality with better specifications in less time and at a lower cost.Several investigations are being performed to evaluate the capacity of these techniques in comparison with the conventional routes [3,4,5]
We explore an additional surface cellular response to SLMed Ti‐6Al‐4V samples
It was shown that using hot isostatic pressing (HIP) resulted in reducing the residual porosity within the SLMed builds as well as, transforming the martensitic needle-like α0 structure in the as-fabricated condition into the α + β structure, which resulted in an improvement of the ductility
Summary
The development of additive manufacturing (AM) techniques has recently gained significant attention for the fabrication of customised implants to the needs of individual patients in healthcare [1,2].This strategy relies on 3D printing of the part from digital models in a layer-by-layer fashion in an attempt to add new implant functionality with better specifications in less time and at a lower cost.Several investigations are being performed to evaluate the capacity of these techniques in comparison with the conventional routes [3,4,5]. The development of additive manufacturing (AM) techniques has recently gained significant attention for the fabrication of customised implants to the needs of individual patients in healthcare [1,2]. This strategy relies on 3D printing of the part from digital models in a layer-by-layer fashion in an attempt to add new implant functionality with better specifications in less time and at a lower cost. Materials 2020, 13, 2813 manufacturing patient-particular metallic implant parts This system uses a high power density laser to melt and fuse the metallic powders according to the CAD model of the implant to form a 3D part in an inert atmosphere preventing the oxidation of the metallic powder in the air [6]. SLM, similar to other AM techniques, can reduce the amount of materials waste, in addition to its disruptive benefits of saving time and cost by skipping many additional manufacturing steps to obtain the final part [7]
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