The component pictured in Figure CS-16 is the impeller of a water pump used by a major

Question:

The component pictured in Figure CS-16 is the impeller of a water pump used by a major automotive manufacturer. The outer diameter of the component is 2.75 in. and the total height of the six curved vanes is 0.75 in. (with a tolerance of 0.005 in.). The inner diameter of the center hole is 0.625 in., and the flat base is 0.187 in. thick. Vibration and balance considerations require accurate positioning and uniform thickness of the six curved vanes. A relatively smooth surface finish is desirable for good fluid flow.
The maximum operating temperature has been estimated at 300°F, and the contact fluid should be a water/antifreeze mixture with corrosion resistant additives. The designer has provided a target tensile strength of 30,000 psi, and notes that a minimum amount of fracture resistance is also desirable. Since there should be no direct metal-to-metal rubbing, enhanced wear resistance does not appear to be necessary. This is a high volume component, however, so low total cost (material plus manufacturing) would appear to be a prime objective.
Similar components have been sand cast from cast iron, with a grinding operation being required to maintain controlled height. The manufacturer is interested in improving quality and lowering cost.
1. Is a ferrous material needed to provide the desired properties, or might a nonferrous metal be acceptable?
2. What processes would you want to consider to mass produce such a shape? Are there more attractive casting processes? Is this a candidate for metal forming, and if so, which process or processes? Is powder metallurgy a possibility for this product? If so, can the desired properties be achieved with the densities that are common for a traditional press and-sinter operation?
3. Investigate the various material-process combinations that would be candidates for production. Select and defend your "best choice."
4. Might this part be a candidate for manufacture from a nonmetal, such as molded nylon, some other polymer, or even some form of reinforced composite material? How would you suggest producing the desired shape if one or more of these materials were considered? Would you have to compromise on any of the performance requirements?