A Breakthrough for Processing of Net-shaped PM Parts using Nanopowders

Abstract

This paper reviews our recent investigations for finding a breakthrough for processing of net-shaped powder metallurgical parts using nanopowders. Especially, the issues on low-temperature powder injection molding of the Fe nanopowder- and micro-nano powder feedstock using a low melting binder are introduced. Relating to consolidation of the nanopowders by pressureless sintering, understanding nanopowder agglomerate sintering (NAS) process is essential to processing of net-shaped nanopowder materials and components. Based upon this concept, we have suggested a new idea of full density processing for fabricating micro-powder injection molded part using metal nanopowder agglomerates produced by hydrogen reduction of metal oxide powders. The debound (brown) part maintained uniform and sound surface structure due to strong networks between the micropowders by enhanced sintering effect of nanopowders during the debinding process. During sintering the PIM gear underwent isotropic shrinkage to reach full density while the micropowder grains rarely grew due to the inhibition effect of the nanopowders on the migration of micropowder grain boundaries. Conclusively, the use of micro-nano powder feedstock might provide a potential application for processing the PIM parts with full density and fine microstructure.