Advancements in Binder Jetting for Metal Matrix Nanocomposites
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Chapter 1: Understanding Binder Jetting Technology
In this article, we will delve into the innovative applications of metal matrix composites that are enhanced by spray adhesives in conjunction with base metals through pressureless melt infiltration techniques. We'll also explore how to determine the best infiltration conditions to establish new operational parameters.
Existing subtractive methods often fall short in producing intricately shaped graphite components that meet specific microstructural and performance criteria. This gap has prompted the development of new additive manufacturing techniques, including selective laser sintering (SLS), stereolithography (SLA), laminated object manufacturing (LOM), and adhesive inkjet printing. Notably, the binder jetting process (BJP) has emerged over the last twenty years as a superior alternative to traditional additive manufacturing approaches.
Due to their high melting points, hardness, and brittleness, ceramic materials pose challenges in processing compared to metals and polymers using additive techniques. When employing a method to create a carbide framework through binder pouring followed by cobalt infiltration, excessive infiltration duration may result in the growth of tungsten carbide grains. The sintering process plays a crucial role in preventing unintended aggregation of these grains. These techniques are applicable not only to metals but also to metal matrix reinforced alloys and composite materials.
Section 1.1: Advantages of the Binder Jetting Process
One of the standout features of the BJP process is its compatibility with standard post-treatment methods, such as reaction sintering or liquid metal infiltration, which are essential for achieving the desired density and mechanical properties. This study aims to investigate the potential for leveraging BJP technology alongside necessary additional treatments, like impregnation and pyrolysis using a binder, to produce graphite components that exhibit low porosity and high density.
Subsection 1.1.1: Carbon Fibers for Enhanced Performance
Carbon fibers are often utilized as reinforcements in both additive metal parts and composites. For instance, carbon fibers integrated into an aluminum matrix yield composites characterized by low density and high strength.
Section 1.2: The Role of Powder Layer Infiltration
A typical microstructure of samples produced via the binder casting and infiltration method is illustrated in the accompanying figure. Metal matrix composites (MMCs) consist of at least two constituent materials, with one being a metal, while the other may be another metal, ceramic, or organic compound.
Using a pycnometer with helium gas, the porosity of the alumina powder layer was determined to be approximately 70% prior to any infiltration experiments. This method ensures that the presence of soft agglomerates in various powder materials does not affect the measurements, as they can easily permeate and yield a porosity that remains unaffected by individual powder size.
Current literature suggests that capillary interactions within the powder are governed by capillary processes. Therefore, real-time monitoring of infiltration offers valuable insights into the mechanisms operating on both spatial and temporal scales.
The data collected can serve to validate fluid penetration kinetics models into the powder bed. However, caution is warranted in analyzing and interpreting saturation levels behind the fluid penetration front, as certain thermal residual stresses can lead to plastic deformation within the die during manufacturing.
Denesuk posits that infiltration initiates at time = 0, assuming a spherical liquid cap is already present on the powder surface. Nonetheless, MMCs are often more costly to produce, and fiber-reinforced materials can be challenging to manufacture, compounded by limited user experience.
As the composite cools to room temperature, residual stresses can manifest due to the differential thermal expansion between the metal matrix and the fiber. Observations show no complexes or third-phase inclusions at the interface, despite the material being subjected to high temperatures during the SEBM process.
Chapter 2: Video Insights on Binder Jetting Technology
This first video explores the advancements in binder jet metal 3D printing, focusing on how innovative binder chemistry is enhancing this technology.
The second video presents a comprehensive webinar on the metal binder jetting process and its various applications, featuring insights from Azoth 3D.