Powder Processes

This chapter focuses on processes that transform a metal, ceramic, or polymer powder into a solid object. Powders can be formed into shapes by processes that involve compaction and thermal treatment for densification, or they can be converted into functional parts by additive manufacturing processes. To understand powder processing better, the chapter begins with an introduction to the powder state, including particle packing and flow, and continues with a discussion of the macroscopic and microscopic changes that occur during “firing” or thermal treatment, including sintering and grain growth. Several processes that involve compaction are covered, including uniaxial pressing, isostatic pressing, and variations that involve heat and pressure. Rotational molding, a process that begins with a thermoplastic polymer powder and ends with a hollow shape, is introduced as well. The chapter concludes with a discussion of powder-based additive manufacturing processes, such as selective laser sintering.