초록 ▼

The shrinkage normally encountered when molding a mixture of spherical cobalt-containing particles and thermoplastic binder, heating the resulting molded article to degrade the binder and form a porous preform, and infiltrating the same is counteracted by adding finely divided elemental iron or elem

The shrinkage normally encountered when molding a mixture of spherical cobalt-containing particles and thermoplastic binder, heating the resulting molded article to degrade the binder and form a porous preform, and infiltrating the same is counteracted by adding finely divided elemental iron or elemental nickel to the spherical cobalt-containing particles. In addition to improving dimensional control, the elemental powder addition increases impact strength while maintaining hardness.

대표청구항 ▼

A shaped, homogeneous, monolithic metal article, comprising: A. a skeleton, comprising (i) a plurality of generally spherical domains having an average diameter less than about 200 micrometers, said domains, when viewed using backscattered electron imaging, comprising granules of chromium carbide ho

A shaped, homogeneous, monolithic metal article, comprising: A. a skeleton, comprising (i) a plurality of generally spherical domains having an average diameter less than about 200 micrometers, said domains, when viewed using backscattered electron imaging, comprising granules of chromium carbide homogeneously dispersed throughout a first solid solution comprising cobalt and chromium; (ii) a second solid solution comprising cobalt and chromium, said second solid solution (a) containing a greater percentage of cobalt and a lesser percentage of chromium than said first solid solution, (b) being essentially free of carbides, and (c) enveloping the majority of said spherical domains, the so-enveloped domains and second solid solution being interconnected to form said skeleton; and (iii) iron or nickel as an additional component of said first and second solid solutions; and B. infiltrant, comprising a continuous phase of metal or alloy occupying the volume of said article not occupied by said skeleton; said skeleton and said infiltrant thereby comprising two intermeshed matrices and said article being substantially void-free. In a process for making infiltrated molded metal articles by molding in a flexible mold of a master a plastic mixture of spherical cobalt-containing powder and heat fugitive binder comprising thermoplastic material to form a green article of predetermined shape and dimensions, removing said green article from said mold, heating said green article to remove said binder and consolidate said spherical cobalt-containing powder in the form of a porous, monolithic skeleton of particles of cobalt-containing metal, infiltrating said skeleton with a molten metal having a melting point that is at least 25°C. less than the melting point of the lowest melting of said cobalt-containing metal particles, and cooling the infiltrated skeleton, the improvement comprising adding to said spherical cobalt-containing powder up to about 11% by weight, based on the weight of said spherical cobalt-containing powder, of elemental iron or elemental nickel particles having an average particle diameter less than about 10 micrometers.