AMES has different shaping and sintering techniques available depending on the part geometry, its functionality, and the material.
Steel sintered components for mechanical or magnetic use require the highest possible density, since microporosity negatively affects their properties. The most common shaping technique is the high pressure uniaxial compacting of the powder within a rigid tool and subsequent sintering in controlled atmosphere at temperatures between 1,100 and 1,300ºC, typically reaching between 86 and 94% of the wrought density (between 6 and 14% porosity by volume). Shaping by additive manufacturing using the Binder Jetting technique combined with more severe sintering conditions makes it possible to achieve more than 98% of the wrought density.
Porosity is the functional parameter of other types of components, and therefore shaping focuses to achieve a specific density or porosity.
Self-lubricating bearings are formed by low pressure uniaxial compacting. Their porosity is between 18 and 25% by volume. Porosity serves to contain the lubricating oil that provides self-lubrication to the shaft-bushing system.
Filters have a porosity between 25 and 60% by volume. Porosity serves mainly to retain particles (filter), cushion pressure, silence, control flow, fluidize or gasify.
Spherical bronze filters are shaped by loose powder, which means filling a mold with powder by gravity and sintering the preform into the mold. This method allows to achieve very complex shapes.
Stainless steel filters are shaped in 3 different ways.
■ Low pressure uniaxial compacting. It is used for filters with simple geometry and small size (discs, rings or plates).
■ Isostatic compacting. It consists of filling a flexible mold with powder and applying pressure on the mold in the 3 space directions through a fluid. This method is used to produce porous tubes of big length and diameter, achieving homogeneous porosity along the entire filter length.
■ Extrusion. It consists of shaping a tube by extruding a paste of metal powder into a cylindrical matrix, This method provides porous tubes of small diameter and wall thickness and big length, suitable for tangential filtration.
Biomedical titanium implants have a higher porosity, around 65% by volume. The porosity serves to promote osteointegration of the implant with the surrounding. This high porosity is achieved by adding spacers to the mixture, which are removed during the process and leave in their place pores of controlled shape and size. Titanium requires high vacuum sintering.
The most porous product manufactured by AMES is metallic foams. They are shaped by impregnation of a polymeric foam with a metallic powder slurry that remains adhered to the base foam. The polymeric foam is removed during sintering, resulting in a metal skeleton with extremely high porosity, between 70 and 90% by volume. Porosity of the foams is used for multiple purposes.
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