Effect of sintering temperature on binder jetting additively manufactured stainless steel 316L: densification, microstructure evolution and mechanical properties

Abstract

Binder jetting (BJ) selectivity jets binders on powders to form green parts efficiently. The following sintering process is indispensable to consolidating as-printed loose parts, inevitably introducing shrinkage and grain growth. The pore morphology and grain size will change significantly in the sintering process, directly affecting the sintered parts' density and mechanical properties. However, there is no research on the microstructure evolution of BJ 316L in the sintering process to date, which is essential for the further application of BJ 316L. This study used a solid state sintering process to consolidate the BJ 316L green parts. The effect of vacuum sintering temperature (1300 °C–1400 °C) on the density, porosity, linear shrinkage, microstructure evolution, and tensile properties of the as-sintered parts was investigated. Results indicated that the sintering temperature significantly affects the properties of the sintered 316L parts. Notably, the grain size and tensile strength strongly correlate with porosity. The sintered 316L parts have a relative density of 92.0% and preferable mechanical properties (ultimate tensile strength of up to 473.7 MPa and elongation of up to 40.22%) after sintering at 1380 °C. The pores in the sintered BJ 316L were distinguished into three types according to pores' size and distribution characteristics. The potential influences of these three types of pores on the properties of the sintered BJ 316L were discussed. This work is engaged in providing a detailed reference for the densification and microstructure evolution of BJ 316L parts.

Keywords

• Binder jetting
• 316L
• Sintering temperature
• Pores formation
• Microstructure evolution
• Strength