Applications

Parts that are candidates for application of CIP originate within the sets (not all inclusive). They are expensive materials such as titanium, tungsten, molybdenum, and tantalum; materials difficult to machine such as tungsten carbide/cobalt, titanium carbide/iron, titanium, and tool steels; complex shapes; hybrid structures such as layered structures of multiple materials or combined porous/dense structures; and intersections of the above. Using titanium and its principal alloy Ti-6Al-4V as materials for illustration, application examples of CIP are shown in the following. Figure 6 shows the shape complexity feature of CIP where a nearly axisymmetric part 125 mm (5 in.) in diameter with round and rectangular inside-diameter features was produced using hard-tooling core mandrels and a net-shape external elastomer mold. The hard-tooled surfaces have evolved as smooth compared to the elastomer mold interface surfaces following CIP plus HIP. The surface produced by the elastomer mold reflects the particle size of the blended powder. In Fig. 7, CIP has been used with blended elemental powders of Ti-6Al-6V-2Sn and Ti-6Al-4V to produce with high material efficiency a hollow cylindrical cup with isotropic (texture-free) mechanical properties using a hard-tool core mandrel. The part has a high surface-area-to-volume ratio. The alternative to the use of CIP is machining from stock with a resulting low part-weight-to-stock-weight yield ratio. In Fig. 8, a series of parts with variable geometry and integral regions of controlled density have been produced using CIP. Powder size distribution can be selected as well as multiple-step CIP to facilitate production of the design. Porosity can range from zero to slightly greater than one minus the tap density of the metal powder, that is, approximately 1 - 0.55/0.65, where 0.55/0.65 is a normal range of powder density, when low-pressure CIP plus low-temperature sintering increases the original powder density slightly. Filters, filter supports, vibration damping, and heat transfer control devices are typical applications for porous parts. Figure 9 illustrates forging preforms in an aluminum alloy (lighter-color part) and a titanium alloy produced by CIP plus sintering. A final part can be produced with a single die set and forging stroke. Preform dimensions can be modified so that the forging operation produces desired effects including: amount and location of plastic strain, final densification, microstructural homogenization, and property enhancement, particularly fracture toughness. In the case of the connecting rods, overall length is maintained in forging. For tubular or solid parts with length-to-diameter (L/D) ratios of 2 or greater CIP can produce parts such as shown in Fig. 10. This part has an L/D of 2.25 with wall thickness of mm (—0.25 in.) with a closed bottom. Similar parts such as tubes, pipes, hydraulic pressure fittings, and vessel liners with thin walls, high L/D ratios, tapered wall thickness, and stepped bores are all practical with CIP technique.

Fig. 6 Complex cold isostatically pressed P/M part made using internal round and square hard-tooling inserts. Courtesy Dynamet Technology
Fig. 7 Closed one end precision bore cylinder. Material-efficient use of blended elemental titanium and alloying powders. Courtesy Dynamet Technology
Fig. 8 Cold isostatically pressed parts with designed regions of controlled density and porosity. Courtesy Dynamet Technology
Fig. 9 Forging preforms cold isostatically pressed with titanium alloy and aluminum alloy powders. Courtesy Dynamet Technology
Fig. 10 200 mm D by 500 mm L thin-wall tube cold isostatically pressed in Ti-6Al-4V powder blend. Courtesy Dynamet Technology
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