Meenashisundaram Ganesh Kumar, Xu Zhengkai, Nai Mui Ling Sharon, Lu Shenglu, Ten Jyi Sheuan, Wei Jun
Metal and Ceramic Forming Group, Singapore institute of Manufacturing Technology, 73 Nanyang Drive, Singapore 637662, Singapore.
Materials (Basel). 2020 Aug 24;13(17):3744. doi: 10.3390/ma13173744.
High porosity (40% to 60%) 316L stainless steel containing well-interconnected open-cell porous structures with pore openness index of 0.87 to 1 were successfully fabricated by binder jetting and subsequent sintering processes coupled with a powder space holder technique. Mono-sized (30 µm) and 30% (by volume) spherically shaped poly(methyl methacrylate) (PMMA) powder was used as the space holder material. The effects of processing conditions such as: (1) binder saturation rates (55%, 100% and 150%), and (2) isothermal sintering temperatures (1000 C to 1200 C) on the porosity of 316L stainless steel parts were studied. By varying the processing conditions, porosity of 40% to 45% were achieved. To further increase the porosity values of 316L stainless steel parts, 30 vol. % (or 6 wt. %) of PMMA space holder particles were added to the 3D printing feedstock and porosity values of 57% to 61% were achieved. Mercury porosimetry results indicated pore sizes less than 40 µm for all the binder jetting processed 316L stainless steel parts. Anisotropy in linear shrinkage after the sintering process was observed for the SS316L parts with the largest linear shrinkage in the Z direction. The Young's modulus and compression properties of 316L stainless steel parts decreased with increasing porosity and low Young's modulus values in the range of 2 GPa to 29 GPa were able to be achieved. The parts fabricated by using pure 316L stainless steel feedstock sintered at 1200 C with porosity of ~40% exhibited the maximum overall compressive properties with 0.2% compressive yield strength of 52.7 MPa, ultimate compressive strength of 520 MPa, fracture strain of 36.4%, and energy absorption of 116.7 MJ/m, respectively. The Young's modulus and compression properties of the binder jetting processed 316L stainless steel parts were found to be on par with that of the conventionally processed porous 316L stainless steel parts and even surpassed those having similar porosities, and matched to that of the cancellous bone types.
通过粘结剂喷射及随后的烧结工艺，并结合粉末占位技术，成功制备出了具有高孔隙率（40%至60%）的316L不锈钢，其具有相互连通良好的开孔多孔结构，孔隙开放指数为0.87至1。单尺寸（30 µm）且体积占比30%的球形聚甲基丙烯酸甲酯（PMMA）粉末被用作占位材料。研究了诸如（1）粘结剂饱和度（55%、100%和150%）以及（2）等温烧结温度（1000℃至1200℃）等加工条件对316L不锈钢零件孔隙率的影响。通过改变加工条件，实现了40%至45%的孔隙率。为进一步提高316L不锈钢零件的孔隙率值，向3D打印原料中添加了30体积%（或6重量%）的PMMA占位颗粒，实现了57%至61%的孔隙率值。压汞法结果表明，所有经粘结剂喷射处理的316L不锈钢零件的孔径均小于40 µm。对于烧结后的SS316L零件，观察到其在烧结过程后线性收缩存在各向异性，其中Z方向的线性收缩最大。316L不锈钢零件的杨氏模量和压缩性能随孔隙率增加而降低，能够实现2 GPa至29 GPa范围内的低杨氏模量值。使用纯316L不锈钢原料在1200℃烧结且孔隙率约为40%制备的零件表现出最大的整体压缩性能，其0.2%压缩屈服强度为52.7 MPa，极限压缩强度为520 MPa，断裂应变率为36.4%，能量吸收为116.7 MJ/m³。经粘结剂喷射处理的316L不锈钢零件的杨氏模量和压缩性能被发现与传统加工的多孔316L不锈钢零件相当，甚至超过了具有相似孔隙率的零件，且与松质骨类型相匹配。
