Anisotropy in AISI 316L produced by Binder Jetting 3D printing: Sintering shrinkage and thermal conductivity

The inhomogeneous particle packing in green parts manufactured by Binder Jetting 3D printing is responsible for the anisotropy in several phenomena and properties. In this work, the anisotropy of the sintering shrinkage and of thermal conductivity of AISI 316L green specimens is investigated. Shrinkage was investigated by dilatometry. Moreover, the dimensional changes, density, and the thermal conductivity of specimens sintered at intermediate temperatures were measured. The microstructure of the specimens was analysed with the standard metallographic. Sintering shrinkage is basically isotropic during the heating step and becomes anisotropic on approaching the sintering temperature at 1370 degrees C when the full density is achieved. A slight anisotropy in the building plane is observed. Contrarily, thermal conductivity is anisotropic during the heating step and becomes isotropic during the isothermal holding at the sintering temperature. Moreover, there is an inverse relationship between thermal conductivity in the debinded specimen and shrinkage. A hypothesis for this indirect correlation is proposed. The role of the large interlayer pores and the aligned pores caused by the ballistic effect of the binder jet is confirmed.