a metal - infiltrated polycrystalline diamond composite tool comprising a plurality of diamond grains forming a continuous polycrystalline diamond matrix , a metallic phase being substantially palladium - free and contiguous to the continuous polycrystalline diamond matrix , wherein the metallic phase interpenetrates the continuous polycrystalline diamond matrix and substantially wets an outer surface of the continuous polycrystalline diamond matrix ; and a working surface . the metallic phase is formed from an infiltrant and a wetting - enhancement layer disposed on the outer surfaces of the diamond particles , with both the infiltrant and wetting - enhancement layer being substantially palladium - free and comprising at least one metal from the group consisting of cobalt , iron , and nickel . the invention also includes a preform for a metal - infiltrated polycrystalline diamond composite tool , the perform comprising a container , a metallic infiltrant source , and a plurality of coated diamonds , each coated with a wetting - enhancement layer and , optionally , an activation layer , both of which are substantially palladium - free . methods of forming the metal - infiltrated polycrystalline diamond composite tool , the preform , and the coated diamond particles used in the tool are also disclosed .