The Long-term Corrosion Behaviors of SLM 316L Stainless Steel Immersed in Artificial Saliva

The Selective Laser Melting (SLM) is an effective method to produce highly corrosion resistant Oral Alveolar Implants (OAI) by changing the scanning speed. Nevertheless, the long-term corrosion behavior of SLM 316L orthodontic bracket alloys in artificial saliva is overlooked in previous studies. In this study, 316L SS samples fabricated by SLM at different scanning speeds (800 mm/s, 1200 mm/s, and 1600 mm/s) were conducted a long-term (90 days) immersion test by being put into artificial saliva with three different pH values (pH 1.5, pH 4, and pH 6). The morphology, XRD and especially corrosion behavior of the samples fabricated by SLM and forging were investigated. The XRD results exhibit that high-speed scanning accelerates the cooling rate and inhibits the δ → γ phase transformation proceeding. Corrosion results show that the corrosion attack induced by pre-existing pores will expand through the crevices and break down the surface structure around the pores, leading to corrosion damage area to expand to several times of the original pore area. Besides, the mean corrosion rate of the sample at a scanning speed of 800 mm/s shows better corrosion resistance in artificial saliva of pH 4 and pH 6. Compared with wrought 316L SS samples, the SLM 316L SS samples had an obvious difference in the performance of corrosion rate and corrosion behaviors.