Direct Observation on the Pore Elimination During Hip

Abstract

Changes of pore size and shape during encapsulation HIP was examined directly with the novel liquid immersion technique, which can reveal great details of micro-structure and characterize flaw-forming defects of micron-size in undensified specimens. The results were supplemented by the pore size measurement with the mercury porosimetry, and compared to the corresponding results for normal sintering. The behavior in the change of pore size and shape was different in HIP and normal sintering. Elimination of large pores of micron-size starts from the beginning of densification in HIP, where as it does not start in initial stage of densification in normal sintering. The shape of large pores changes drastically in HIP, but hardly changes in normal sintering. These observations were discussed in terms of current sintering theory.