Chapter 7: Powder Metallurgy Processing

Gas turbine disks made from nickel-base superalloys are often produced using powder metallurgy (P/M) techniques because the alloy compositions normally used are difficult or impractical to forge by conventional methods. This chapter discusses the P/M process and its application to superalloys. It describes the gas, vacuum, and centrifugal atomization processes used to make commercial superalloy powders. It explains how the powders are consolidated into preforms or billets using hot isostatic pressing, extrusion, or a combination of the two. It also provides information on spray forming and consolidation by atmospheric pressure, and includes a section on powder-based disk components, where it discusses the general advantages of P/M as well as the effects of inclusions, carbon contamination, and the formation of oxide and carbide films due to prior particle boundary conditions. The chapter concludes with a detailed discussion on mechanically alloyed superalloy compositions, the product forms into which they are made, and some of the applications where they are used.