Binder jet 3D printing – Process parameters, materials, properties, and challenges

As a non-beam-based additive manufacturing (AM) method, binder jet 3D printing (BJ3DP) is a process where a liquid binder is jetted on layers of powdered materials, selectively joined and then followed by densification process. Among AM technologies, binder jetting holds distinctive promise due to possibility of rapid production of complex structures to achieve isotropic properties in the 3D printed samples. By taking advantage of traditional powder metallurgy, BJ3DP machines can produce prototypes in which material properties and surface finish are similar to those attained with traditional powder metallurgy. Various powdered materials have been 3D printed, however, a typical challenge during BJ3DP is developing printing and post-processing methods that maximize part performance. Therefore, a detailed review of the physical processes during 3D printing and the fundamental science of densification after sintering and post heat treatment steps are provided to understand the microstructural evolution and properties of binder jetted parts. Further, to determine the effects of the binder jetting process on metallurgical properties, the role of powder characteristics (e.g. morphology, mean size, and distribution), printing process parameters (e.g. layer thickness, print orientation, binder saturation, print speed, and drying time), sintering (e.g. temperature and holding time) and post-processing are discussed. With the development of AM technologies and need for post-processing in 3D printed parts, it is necessary to understand the microstructural evolution during densification process and here, processing steps are explained. Finally, opportunities for future advancement are addressed.