Methods of manufacturing gradient composite metallic structures

Abstract

A method is disclosed for forming roller cutters and also for forming cutting teeth for rolling cutter bits, including cutter inserts, cutter teeth formed in place, or formed separately and welded in place, etc., by powder metallurgy as a densified powder metallurgical composite of at least two varying phases, the composite having a substantially continuous mechanical property gradient therethrough. The gradient is from one region having hardness or wear resistant properties to another region having toughness properties. The method comprises:providing a first powder mixture comprising a major proportion by volume of a powdered refractory compound and a minor proportion by volume of a powdered binder metal or alloy. Providing a second powder comprising a powdered binder metal or alloy or a mixture comprising a powdered refractory material and a powdered binder metal or alloy, present in a lesser proportion by volume than in the first powder. Forming the cutter, or cutter teeth or inserts of the first and the second powders. Mixing the powders during or prior to the forming step and introducing into a first region of the mold a mixture having a larger proportion of the first powder relative to the second powder. Changing the relative proportions of the powders and introducing the mixture into a second region of the mold a mixture having a different proportion of the first powder relative to the second powder and a continuous gradient in the relative proportions of the powders between the regions. Densifying the powders into a solid member having a gradient in composition and properties from the first region to the second region.