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J.L. Johnson, L.K. Tan, R. Bollina, P. Suri, and R.M. German, “Bi-Metal Injection Molding of Tough/Wear-Resistant Components,” Advances in Powder Metallurgy and Particulate Materials, R. Lawcock and M. Wright (eds.), MPIF, Princeton, NJ, 2003, pp. 8.234-8.244.



    Bi-material components can be processed by MIM by two-color injection molding and co-sintering, but compositions and sintering cycles must be optimized to minimize shrinkage mismatch while providing the desired properties. The effects of sintering temperature on the sintered density, hardness, and mechanical properties of M2 tool steel and boron-containing 316L stainless steel are investigated. The compatibility of co-sintering these materials is predicted based on calculations of the thermal stress and strength of the component during sintering. This prediction is verified by successful Bi-MIM processing of 316L-0.5B stainless steel/M2 tool steel components for applications that require a combination of toughness and wear resistance.



    Boron additions of 0.5 wt.% enhance the sintering of 316L stainless steel such that it has similar densification behavior to M2 tool steel. Strength, density, and hardness after sintering 316L-0.5B at 1245°C are all improved in comparison to 316L sintered at 1330°C. Ductility is reduced to 15%, but this is still acceptable for many applications. M2 sintered at 1245°C shows high strength and can achieve a hardness of 59 HRC after heat treating. The hoop stresses generated during co-sintering of M2 and 316L-0.5B concentric rings do not exceed the strengths of the materials, allowing for the fabrication of demonstration Bi-MIM components with a unique combination of wear resistance and toughness.

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