Estudo da sinterabilidade de pastas à base de níquel e suas ligas para manufatura aditiva por extrusão

Abstract

In this study, samples based on nickel metallic pastes were manufactured, both with and without the addition of alloying elements (niobium and copper). These samples were compacted and molded to evaluate their properties through mechanical tests (Vickers hardness and compression tests), microstructure analysis, and an examination of the behavior of the paste formed between the metal powder and binders (PVA2, PVA7, CMC2, PEG7.5+PVA3.5). The aim was also to select the optimal paste for subsequent printing using the additive manufacturing technique through extrusion. In the first phase, six groups of pastes were prepared, each with a different chemical composition, varying the metal powder or the binder. The binder’s function was to provide the paste with pseudoplastic characteristics and improve its printability. Among all the groups analyzed after undergoing the sintering heat treatment, samples containing pure nickel coated with oleic acid and 30% binder (PVA7.5+PEG3.5 solution in distilled water) exhibited mechanical properties typical of metallic materials. These included an average yield strength of 176.3±14.2 MPa, a compression rupture strength exceeding 1200 MPa, and a deformation of approximately 67%. Moreover, these samples displayed advanced sintering stages through microstructural analysis, with low oxygen content and minimal porosity (1.1±0.5%). Regarding observations of the molded samples, almost all pastes showed suitable characteristics for printing test specimens, with separation of the binder and metal powder only observed in the first group. In the second phase, the selected paste was used to 3D print various test models designed in Solidworks. While some printed samples exhibited slight deviations from the CAD model, others closely approached the expected results. Sintering of the samples was conducted with characteristics analogous to the same group of compacted samples to maintain greater reliability for property comparisons. The results revealed high porosity and the presence of oxides in the microstructure, necessitating adjustments in the operating temperature to achieve ideal mechanical properties for future applications.