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J.L. Johnson, L.K. Tan, P. Suri, and R.M. German, “Design Guidelines for Processing Bi-Material Components via Powder Injection Molding,” JOM, vol. 55, no. 10, 2003, pp. 30-34.

 

Abstract

    Powder injection molding can be used to fabricate bi-material components that provide unique functionality, such as a combination of toughness and wear resistance. Successful processing of these components requires minimization of internal stresses during sintering. The stresses generated during co-sintering of concentric rings are analyzed, compared to the materials’ strengths, and correlated with defects. The results provide guidelines for determining the compatibility of various materials and the effect of component geometry.

 

Conclusions

    Successful processing of bi-material components requires that the interfacial strength exceed the maximum radial stress and that the in situ material strength exceed the maximum tensile hoop stress. These requirements can be met if the following conditions exist.

  1. Metallurgical bonding between materials

Using materials with similar compositions and powder characteristics can ensure good bonding. Small modifications (less than 25%) to the powder can be used to tailor properties. This ease of modifying compositions is one of the main advantages of using PIM technology in producing metallic parts.

  2. Shrinkage match between the two materials

Co-sintering materials requires that they have similar densification behavior. Minor chemistry changes can significantly alter a material’s shrinkage behavior, making it more compatible for co-sintering. Shrinkage can also be adjusted by modifying the solids loading of the feedstock.

  3. Component geometry that minimizes internal stresses

Performing stress calculations on a component can identify potential design changes to reduce the likelihood of cracking. Some design changes may not affect the external dimensions of the part, making them relatively easy to implement.

Metal Injection Molding of Co-28Cr-6Mo