Abstract
To fabricate metallic 316L/HA (hydroxyapatite) materials which meet the requirements of an implant’s mechanical properties and bioactivity for its function as human bone replacement, selective laser melting (SLM) has been employed in this study to prepare a 316L stainless steel matrix, which was subsequently covered with a hydroxyapatite (HA) coating using the sol-gel method. High density (98.9%) as-printed parts were prepared using a laser power of 230 W and a scanning speed of 800 mm/s. Austenite and residual acicular ferrite existed in the microstructure of the as-printed 316L stainless steel, and the sub-grain was uniform, whose primary dendrite spacing was around 0.35 μm. The as-printed 316L stainless steel showed the highest Vickers hardness, elastic modulus, and tensile strength at ~ (~ means about; same applies below unless stated otherwise) 247 HV, ~214.2 GPa, and ~730 MPa, respectively. The elongation corresponding to the highest tensile strength was ~38.8%. The 316L/HA structure, measured by the Relative Growth Rate (RGR) value, exhibited no cell cytotoxicity, and presented better biocompatibility than the uncoated as-printed and as-cast 316L samples.
Highlights
With the continual progress of medical technology as well as the extension of human life, it is probable that there will be a huge potential demand for and research interest in metallic body implants [1,2]
The cell viability on the 316L/HA samples and the as-printed samples is significantly higher than the as-cast samples. These results indicate that all the samples present no cell cytotoxicity according to the Relative Growth Rate (RGR)
Compared with the 316L/HA and the as-printed 316L stainless steel, the cells cultured on the as-cast samples shown in Figure 13c exhibit a near-round shape with less spreading
Summary
With the continual progress of medical technology as well as the extension of human life, it is probable that there will be a huge potential demand for and research interest in metallic body implants [1,2]. It has been used to successfully prepare many kinds of metallic biomaterials, such as stainless steel, alloys of titanium, magnesium, and medical noble metals, and compared with some of the more traditional approaches, it provides superior mechanical properties and a relatively simpler manufacturing process [19,20]. In order to testify its feasibility as an implant, simple cytotoxicity and biocompatibility tests were conducted while comparing different manufacturing and post-processing methods [24,25,26,27,28]. These can hardly solve the problem of poor bioactivity, and may even cause a failure of metallic implants. This study demonstrates that it is possible to enhance the bioactivity of the as-printed 316L steel by HA coating
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