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Hot Forming of Ceramics

  • Roy W. Rice
Part of the Sagamore Army Materials Research Conference Proceedings book series (SAMC, volume 15)

Abstract

This chapter discusses hot-consolidation of ceramic powders with and without additives, and hot working of ceramic bodies. Hot consolidation (e.g., by hot pressing) of powders without sintering additives is shown to generally produce the finest grain sizes. The resultant bodies generally have the highest strengths to several hundred degrees Kelvin. Additives such as LiF and NaF to oxides (e.g., MgO, CaO, and Al2 O3) and of metals (molten at pressing) to carbides are shown to often aid consolidation and formability (e.g., allowing hot rolling). However, the use of such additives also often leads to some penalties such as greater grain growth or lower elevated temperature strengths. The major problem of hot consolidation of oxides, with or without additives, is shown to be removal of the last traces of impurities such as H2O and CO2, which are usually present in reacted form (e.g., hydroxides and carbonates), while other anion impurities may cause problems in carbides and borides.

Hot working (i.e., causing plastic deformation within grains) is discussed both for starting with solid bodies, and starting with powders where consolidation and working are done in the same operation. Neither method has yet produced bodies of as fine a grain size as can be achieved by hot pressing. However, elevated temperature strengths of some hot worked bodies are shown to be much-greater than those achieved by hot pressing. These higher strengths result from hot working bodies with substantially reduced anion impurity levels, as well as obtaining both texturing and slower grain growth in the hot worked bodies. Other advantages (e.g., improved optical properties) may also be obtained by hot working.

Possible solutions to the problems of impurities left after consolidation and of reducing grain sizes of hot worked bodies are discussed. Obtaining powders with more controlled composition and finer particle and agglomerate sizes will help both problems. Some comments on the means of obtaining such powders are briefly outlined.

Keywords

Gaseous Impurity Pressure Sinter Hydrostatic Extrusion Tantalum Carbide Elevated Temperature Strength 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Syracuse University Press Syracuse, New York 1970

Authors and Affiliations

  • Roy W. Rice
    • 1
  1. 1.The Boeing CompanySeattleUSA

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