Cegan Tomas, Pagac Marek, Jurica Jan, Skotnicova Katerina, Hajnys Jiri, Horsak Lukas, Soucek Kamil, Krpec Pavel
Faculty of Materials Science and Technology, VSB-Technical University of Ostrava, 70800 Ostrava, Czech Republic.
Faculty of Mechanical Engineering, VSB-Technical University of Ostrava, 70800 Ostrava, Czech Republic.
Materials (Basel). 2020 Oct 1;13(19):4377. doi: 10.3390/ma13194377.
The manufacturing route primarily determines the properties of materials prepared by additive manufacturing methods. In this work, the microstructural features and mechanical properties of 316 L stainless steel prepared by the selective laser method have been determined. Three types of samples, (i) selective laser melted (SLM), (ii) selective laser melted and hot isostatic pressed (HIP) and (iii) selective laser melted and heat treated (HT), were characterized. Microstructural analysis revealed that SLM samples were formed by melt pool boundaries with fine cellular-dendritic-type microstructure. This type of microstructure disappeared after HT or HIP and material were formed by larger grains and sharply defined grain boundaries. The SLM-prepared samples contained different levels of porosity depending on the preparation conditions. The open interconnected LOF (lack of fusion) pores were observed in the samples, which were prepared with using of scanning speed 1200 mm/s. The blowhole and keyhole type of porosity were observed in the samples prepared by lower scanning speeds. The HIP caused a significant decrease in internal closed porosity to 0.1%, and a higher pressure of 190 MPa was more effective than the usually used pressure of 140 MPa, but for samples with open porosity, HIP was not effective. The relatively high yield strength of 570 MPa, tensile strength of 650 MPa and low ductility of 30-34% were determined for SLM samples with the lower porosity content than 1.3%. The samples after HIP showed lower yield strengths than after SLM (from 290 to 325 MPa) and relatively high ductility of 47.8-48.5%, regardless of the used SLM conditions.
制造工艺路线主要决定了通过增材制造方法制备的材料的性能。在这项工作中，已经确定了通过选择性激光方法制备的316L不锈钢的微观结构特征和力学性能。对三种类型的样品进行了表征：（i）选择性激光熔化（SLM）；（ii）选择性激光熔化并热等静压（HIP）；（iii）选择性激光熔化并热处理（HT）。微观结构分析表明，SLM样品由具有精细胞状树枝晶型微观结构的熔池边界形成。这种微观结构在HT或HIP处理后消失，材料由更大的晶粒和清晰界定的晶界形成。根据制备条件，SLM制备的样品含有不同水平的孔隙率。在使用扫描速度为1200mm/s制备的样品中观察到开放互连的未熔合（LOF）孔隙。在较低扫描速度制备的样品中观察到气孔和匙孔型孔隙。HIP使内部封闭孔隙率显著降低至0.1%，190MPa的较高压力比通常使用的140MPa压力更有效，但对于具有开放孔隙率的样品，HIP无效。对于孔隙率含量低于1.3%的SLM样品，测定了相对较高的屈服强度570MPa、抗拉强度650MPa和较低的伸长率30 - 34%。无论使用何种SLM条件，HIP处理后的样品屈服强度均低于SLM处理后（从290到325MPa），且伸长率相对较高，为47.8 - 48.5%。
