Net shape components

Evaluate feasible fabrication routes which yield either a semifinished product (strip, wire, etc.) or even near-net shaped components. 

Shape Manufacturing AN APPROACH TO NEAR-NET- 564 3.4. Semihot-fonned Near-Net- Shape Components Examples 580... 

Semihot-formed Near-Net-Shape Components Examples of Applications... 

Hot isostatic pressing can provide a uniform high density, to almost 100% of theoretical density, providing near net shape components without size limitations. Since the applied pressure is uniform, the density too is uniform. The process can be used directly, or in combination with a preforming step such as injection molding or sintering. The technique has been described in relation to carbon-carbon composites (Chapter 14, Section 14.3.3.3). 

Carbon fiber is used in continuous and chopped fiber form and can be made into a preform to obtain near net shape components. The preform can be held together with a binder such as an acrylic polymer or aluminum metaphosphate [4-6]. The more expensive... 

A modification of melt stirring, termed compocasting (or rheocasting), is used to obtain a suitable slurry by employing powerful agitation of a semisolid (two phase) alloy to yield a non-dendritic phase, which imparts thixotropic properties. The mix is then infiltrated to produce a near net shape component [138-139]. It is desirable that the alloy has a wide solidification range in which it exists as a semisolid. The volume fraction of carbon fiber is restricted to about 20% to obtain effective dispersion. 

The BE approach has found a niche for the production of near-net-shape components or of low-cost preforms for subsequent processing, such as forging. Applications include sidewinder missile housing, missile fins, connecting rods, turbine blade preforms, hex stock preforms for fittings, nuts, mirror hubs, and lens housings. 

Various processes under the heading of cold forming tend to combine forward and backward extrusion to produce near-net shaped components by the application of high pressures and forces (see 3.4F). 

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