Nickel-based Alloy Research
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Metal Injection Molding of Co-28Cr-6Mo
J.L. Johnson and E.J. Westcot, “Metal Injection Molding of Commercially Pure Nickel for the Chemical Processing Industry,” Inter. J. of Powder Metall., vol. 39, no. 8, 2003, pp. 37-45.
Commercially pure Ni is used in the chemical processing industry for components that are subjected to reducing aqueous conditions. A spherical -10 µm Ni powder was evaluated for its suitability to produce such components by metal injection molding (MIM). This powder was mixed with a polymer-wax binder. Both tensile bars and rectangular bars were injection molded. Sintering optimization of debound tensile bars resulted in high sintered densities and mechanical properties comparable to commercially pure Ni alloy Ni270. For comparison in corrosion tests, 316L stainless steel rectangular bars were injection molded from a gas atomized -22 µm powder. Corrosion testing of both MIM Ni and MIM 316L rectangular bars was performed in a variety of media, including nitric acid, hydrochloric acid, bleach, sodium hydroxide, sulfuric acid, and ferric chloride solution. The results show that MIM Ni is better suited for reducing corrosive environments, such as sodium hydroxide and intermediate strength sulfuric acid, than MIM 316L, which is analogous to their wrought behavior.
Metal injection molding can be used to process commercially pure Ni with mechanical and corrosion properties comparable with handbook values. A spherical Ni powder with a particle size less than 10 µm provides the required combination of rheological behavior and sintering response to achieve these properties with metal injection molding. The general corrosion resistance of commercially pure MIM Ni is significantly better than that of MIM 316L stainless steel in 40% sodium hydroxide and 50% sulfuric acid. Thus, MIM Ni is more suitable for certain applications in the chemical processing industry.