Effects of part size on densification and microstructure of 17-4 PH stainless steel printed by binder jetting additive manufacturing

Le résumé fourni par la source

Binder jetting additive manufacturing is a powder-bed 3D printing method that offers material and cost savings, high scalability, and compatibility with a wide range of materials such as metals and ceramics. The absence of high temperature during the printing process can reduce the probable thermal distortion and defects such as residual stress, and cracking. However, inadequate studies in this area and lack of comprehensive understanding of material properties, limit its wide adoption in the industry. This study aims to investigate the effects of part size on the sintering geometry and microstructure of binder jetting printed 17-4 PH stainless steel parts. Cuboid-shaped samples were printed in four different lengths to assess the effect of size on part densification and microstructures. The anisotropic shrinkage was examined for different sizes and buildup directions, and its influence on the part sintering. It is found that the both before-sintering and after-sintered densities of sample increase with the sample size from 5 mm to 20 mm. The average density increment is 43 % for 20 mm sample in contrast to the 37 % increase for smaller size of 5 mm. Anisotropic shrinkage happens in larger sample of 20 mm, with a significant variation in the buildup and horizontal directions. However, the anisotropic shrinking is more homogenous for the size less than 15 mm. Furthermore, the microstructure of before-sintering and after-sintered samples was revealed using scanning electron microscopy (SEM). It is revealed that the cleavage fracture and dimple texture occurred on the fracture surface, indicating both the brittle and ductile properties of materials. The SEM images of before-sintering and after-sintered samples show the powder sintered porosity and crack defects. The higher porosity level is revealed in smaller sample sizes compared to bigger ones.

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