Understanding the HIP (Hot Isostatic Pressing) Consolidation of P/M Nickel-Base Superalloys.
Annual summary rept. 1 Oct 84-30 Sep 85,
COLUMBIA UNIV NEW YORK
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Hot isostatic pressing HIP to near-net shape is the most cost effective method of superalloy powder consolidation. However, as-HIP superalloys have been plagued by poor mechanical properties which can be ascribed, in parts to prior particle powder boundaries PPB. The solution to this problem pivots about altering the deformation mechanism comprising HIP densification to minimize PPB. Since commercial powder consists of particles of unequal size, a variation in the extent of deformation is seen--small particles are smeared between large particles which remain relatively undeformed. The undeformed boundaries or PPB are sites for precipitation of blocky gamma prime and deleterious carbides. This research seeks to advance scientific understanding of HIP and to apply that understanding to HIP processing. HIP runs were done at one commercial pressure and temperature 1120 C and 103 MPa for varying hold times and for three different size distribution of powders monosized -170 200, bimodal 80 -170 200, 20 - 400 500, and full size -150 mesh. Contrary to industrial belief, densification was nearly instantaneous. These deformation mechanisms were mainly athermal plastic flow rather than creep deformation. Rapid deformation andor full size powder distribution led to a greater density of PPB. Consolidation at atmospheric pressure CAP runs were also conducted at two temperatures for varying hold times.
- Metallurgy and Metallography