Cemented carbide-steel composites for earthmoving and mining applications

The method of making a composition of material comprising sintered carbide-binder metal alloys in which the carbide comprises grains of monocarbide based substantially on a preselected hexagonal solid solution (Mo,W)C embedded in a binder of heat treatable steel alloy which contains between 0.40 and 8.0 percent by weight chromium, between 0.40 and 8.0 percent by weight of a metal selected from the group consisting of molybdenum and tungsten less than 1.5 percent by weight vanadium and between 0.15 and 1.20 percent by weight carbon, with the binder metal being from 30 to 80 percent by volume of the composition of material, which method comprises the steps of:

• preparing a powder mixture of binder and carbides having the desired gross composition in which the binder portion of the powder mixture comprises iron powder whose average diameter is less than 40 micrometers alloyed with up to 10 percent by weight other iron group elements and not more than 0.2 percent by weight vanadium and 1.5 percent by weight chromium, with any additional chromium and vanadium being added to the powder mixture as carbides and with molybdenum and tungsten components of the binder being added as elemental powders or carbides,
• wet milling the powder mixture to increase the sintering activity of the iron powder,
• drying and homogenizing the powder mixture,
• pressing the powder mixture into compacts having the desired shapes, and
• sintering the compacts to substantially full density at sintering temperatures not higher than the temperature at which .eta.-carbides are formed for the preselected solid solution (Mo,W)C.

The method of making a heat treatable composite structure comprising a heat treatable cemented carbide component and a heat treatable steel component in which the cemented carbide component comprises grains of monocarbide based substantially on a preselected hexagonal solid solution (Mo,W)C embedded in a binder of heat treatable steel alloy which contains between 0.40 and 8.0 percent by weight chromium between 0.40 and 8.0 percent by weight of a metal selected from the group consisting of molybdenum and tungsten less than 1.5 percent by weight vanadium and between 0.15 and 1.20 percent by weight carbon, with the binder metal being from 30 to 80 percent by volume of the composition of material, and in which the steel component is formed from a castable low alloy steel, which method comprises the steps of:

• preparing a powder mixture of binder and carbides having the desired gross composition of the cemented carbide component in which the binder portion of the powder mixture comprises iron powder whose average diameter is less than 40 micrometers alloyed with up to 10 percent by weight other iron group elements and not more than 0.2 percent by weight vanadium and 1.5 percent by weight chromium, with any additional chromium and vanadium being added to the powder mixture as carbides and with molybdenum and tungsten components of the binder being added as elemental powders or carbides,
• wet milling the powder mixture to increase the sintering activity of the iron powder,
• drying and homogenizing the powder mixture,
• pressing the powder mixture into a compact having a predetermined shape,
• sintering the compact to substantially full density at sintering temperatures not higher than the temperature at which .eta.-carbides are formed for the preselected solid solution (Mo,W)C,
• placing the sintered compact in a predetermined location of a casting mold,
• pouring molten low alloy steel into the mold, and
• allowing the molten steel to solidify, whereby a composite structure is formed in which the cemented carbide component is integrally bonded to the steel component and the cemented carbide component is prestressed in compression.