Modelling and numerical simulation of Supercritical CO2 debinding of Inconel 718 components elaborated by Metal Injection Molding

Abstract

Featured Application: The numerical simulation of the debinding step by using a supercritical fluid is used to predict the binder extraction to optimize the component's shape.Abstract: A debinding step using the supercritical state of a fluid has been increasingly investigated for extracting organic binders from components obtained by metal-injection molding. It consists of placing the component in an enclosure subjected to pressure and temperatures higher than the critical point to perform polymer extraction of the Metal-injection molding (MIM) component. It is an alternative to conventional solvent debinding. The topic of this study is to model and simulate the supercritical debinding stage to elucidate the mechanism of polymer degradation and stabilization with a three-dimensional model. Modelling this extraction process would optimize the process on an industrial scale. It can be physically described by Fick's law of diffusion. The model's main parameter is the diffusion coefficient, which is identified by using linear regression based on the least-squares method. In the model, an effective length scale is specially developed to take into account the diffusion in all directions. The tests were performed for extracting polyethylene glycol, an organic additive, using supercritical CO 2 in injected components. The feedstock is composed of polypropylene, polyethylene glycol, and stearic-acid as binder mixed with Inconel 718 super-alloy powders. The identified parameters were used to calculate the diffusion coefficient and simulate the supercritical debinding step on the Comsol Multiphysics ® finite-element software platform to predict the remaining binder. The obtained numerical simulation results are in good agreement with the experimental data. The proposed numerical simulations allow for the determination of the remaining polyethylene glycol (PEG) binder distribution with respect to processing parameters for components during the supercritical debinding process at any time. Moreover, this approach can be used in other formulation, powder, and binder systems.

Experimental Study on Metal Parts under Variable 3D Printing and Sintering Orientations Using Bronze/PLA Hybrid Filament Coupled with Fused Filament Fabrication

“…It is widely used in many industries, such as mechanical engineering, the automotive industry, aerospace, the electrical industry, etc. [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. Nevertheless, the process has some disadvantages that stand in the way of economical and agile production.…”

“…Generally, there are three types of debinding processes: catalytic debinding [ 8 , 19 ], solvent debinding [ 8 , 11 , 22 ], and thermal debinding [ 3 , 5 , 8 , 14 , 23 ]. In the catalytic debinding process, the binder polyacetal (POM) is broken down into formaldehyde using gaseous nitric acid.…”

An Automated Open-Source Approach for Debinding Simulation in Metal Extrusion Additive Manufacturing

“…for one-dimensional diffusion, where is the concentration of the diffusing component, is the diffusion direction and is the time [17]. The thermal debinding process can be simulated using thermokinetic analysis; therefore, a conversion function U can be defined as follows U , , , , In order to be produced on the machine equipment, the filament must meet various requirements, such as suitable viscous properties.…”

Experimental and numerical analysis of effects of supercritical carbon dioxide debinding on Inconel 718 MIM components

“…However, the extraction of the binder should not damage the component. Agne et al [31] modelled the process using finite element method with this binder on Inconel 718 component, the polymer extraction mechanism, and their numerical results by taking into account the shape of the MIM component and the diffusion coefficient of the soluble binder. Their optimal conditions, in terms of the temperature and pressure of supercritical debinding, were obtained in this study.…”

“…During supercritical debinding, three phenomena may induce dilatation or shrinkage and stress inside the component: the swelling due to polymer extraction, the effect of the high pressure of the supercritical fluid on the component, and the thermal expansion. The shrinkage measured after supercritical debinding is negligible (less than 1%) [31]. The swelling behaviour due to the binder diffusion can also be neglected.…”