Process development of NiTi using binder jetting additive manufacturing: Investigation of the sintering process

Binder jetting additive manufacturing (AM) has emerged as a promising technique for mass-producing items, especially when using metallic materials that are challenging to fabricate in alternative AM processes such as laser powder bed fusion (LPBF). The binder jetting process has the advantage of not involving melting and solidification, which makes it a potential solution for materials such as NiTi shape memory alloys. This approach offers key benefits, including enhanced reliability and isotropic material properties. Recent studies of these alloys in LPBF, while generating promising results, have highlighted the significant costs and technical challenges. This paper presents the first investigation of binder jetting of NiTi, addressing critical aspects of materials and processing, including powder characteristics, binder properties, and process parameters. More specifically, this study explores detailed analyses of powder properties, binder characteristics determined through thermogravimetric analysis (TGA), and the optimization of binder saturation levels. The curing, debinding, and sintering processes were examined in terms of furnace conditions, atmospheres, and temperatures to ensure precise control over the final material properties. Findings from elemental analysis during debinding and a comprehensive evaluation of sintered NiTi components, including density measurements, optical microscopy, backscattered electron (BSE) imaging, elemental analysis, and differential scanning calorimetry (DSC), are presented. These insights are essential for optimizing the mechanical and structural characteristics of the manufactured NiTi alloy components. The results of this paper will be crucial in the optimization of critical parameters to produce high-quality NiTi components with tailored mechanical and thermal properties, opening new horizons for their applications across diverse industries.