Dual-alloy disk system

摘要

Two pieces of metal are bonded together at a surface by placing the two pieces into contact at the surface and forging the two pieces in a die which causes substantial displacement of the metal originally at the surface in a direction parallel to and outwardly from the edges of the surface. In this way, many of the defects which are potentially present at the original surface are displaced with moving metal away from the original contact between the two pieces of metal into sacrificial ribs and the remaining defects are exposed to significant strain. A portion of the displaced metal which contains many of the defects and which forms the sacrificial ribs is removed from the resulting bonded work piece as the sacrificial ribs are removed from the work piece. The result is a bond with superior properties and with a bond surface which can be located very precisely. This system is particularly appropriate for forming dual-alloy high-pressure turbine disks for gas turbines in which an annular peripheral ring of a second super-alloy is bonded to a central core of a first super-alloy. The system is particularly effective if, prior to forging, surfaces to be bonded are closely shape-conforming, are very clean, and are diffusion-bonded using hot isostatic pressing while the surfaces are gas-free. The sacrificial ribs are formed by vents in the impression of the forging dies. The vents are adjacent to the outer edges of the bond surface. The system may be accomplished by using one or more strikes of the same dies, or may include multiple strikes in which only one side of the bond is vented during each strike.