Feedstocks of Aluminum and 316L Stainless Steel Powders for Micro Hot Embossing

Abstract

In metal powder, shaping the preparation and characterization of the feedstock is an aspect commonly recognized as fundamental. An optimized composition is required to ensure the successful shaping of the feedstock. In this study, a commercial binder system, pure aluminum and 316L austenitic stainless-steel powders were used for micro hot embossing. The optimization process revealed that powder characteristics such as shape and the stability of the torque mixing, were important parameters. Manipulating the feedstock composition by adding multi-walled carbon nanotubes or stearic acid or using a higher powder concentration considerably influenced the torque mixing values. The steady state of torque mixing was achieved for all feedstocks. This torque behavior indicates a homogeneous feedstock, which was also confirmed by microscopic observations. Nevertheless, an extruding process was required for greater homogeneity of the aluminum feedstocks. The presence of the carbon nanotubes increased the homogeneity of green parts and reduced microcrack formation. The roughness was essentially dependent on the feedstock composition and on the plastic deformation of the elastomer die. Shaping the prepared feedstocks (with or without carbon nanotube) was achieved by the optimized powder concentrations and it did not increase by the stearic acid addition.

Development of Metal Powder Hot Embossing: A New Method for Micromanufacturing

“…A feedstock is a mixture of powder and binder, at a specific powder concentration, which enables the shaping of very small parts/components with rather complex configurations, as applied in the µ-PIM process. The purpose of a mixture, production of a feedstock, is to disperse the powder in the binder without internal porosity and agglomeration, that is, to obtain a homogeneous biphasic mixture of powders and polymeric binders, and each metallic particle should be covered with a thin layer of binder [16,17]. The characteristics of the feedstock are dependent on the powder and binder characteristics and on the mixing process.…”

“…Multistep melting and complete decomposition of M1 at 500 • C. Increasing PL and adding MWCNT increased the mixing torque value. [9,16,29] PW based with pore-filler polymer 316L powder. DSC and TG to determine the decomposition temperature of the polymer.…”

“…With the growing industrial importance of metal matrix composites, these advanced materials have also been processed by metal powder micromanufacturing processes. Recently, the addition of MWCNT (multiwalled carbon nanotubes) to aluminum and stainless feedstocks for powder hot embossing process has been reported [16]. MWCNTs were mixed with the powders before the preparation of the feedstock.…”

“…For example, the mixing torque values increase with raising mixing speed (up to 100 rpm) or with increasing powder or PP content [22,23]. In addition, the reduction of the mixing torque was correlated with adding SA, PW or with temperature increasing [16,22,23,26]. Table 3 summarizes the various approaches implemented to determine the CPVC and PL values during the powder hot embossing process.…”

“…The four feedstock revealed torque values < 2N [30] Gradual addition procedure during mixing torque CPVC = 62% PL = 60% [8,13,24,27] Gradual addition procedure during mixing torque 16,29] Gradual addition procedure during mixing torque CPVC = 62% PL = 60% [34] The value of the powder and binder content in feedstock (determined as PL) also affects the performance of debinding and sintering. An excess binder does not retain the shape after debinding [32].…”