Warm-Hip Compaction of Attrition-Milled Iron Alloy Powders
J C. Rawers, Frank S. Biancaniello, Rodney D. Jiggetts, Richard J. Fields, Maureen E. Williams
Warm-HIP (Hot-Isostatic-Pressure) compaction of attrition-milled iron alloy powders resulted in production of high strength, fully-dense compacts of nanostructured iron alloy powders. Commercial development of nanostructured materials has been largely restricted because of the (i) limited quantities of starting nanostructured materials, and (ii) limited processing technologies capable of producing fully-dense compacts, and (iii) difficulty in retaining the nanostructure during compaction (1,2,3). High-energy ball milling of powders can now provide kilogram quantities of nanonstructured materials, overcoming the production limitations of the starting powders (4). HIP compaction is capable of producing near-net-shape fully-dense compacts of powder (5). Warm-HIP is defined as hot-isostatic-pressure compaction with the processing temperature under 0.5 Tm.p., a sufficiently low temperature to retard atomic diffusion and retard grain growth. The application of both elevated pressures and temperatures during WARM-HIP assures that the milled particles undergo plastic deformation, and the bonding between particles, largely by surface diffusion, results in chemical bonding. Characterization and results of Warm-HIP compacted nanostructured iron powder alloys are presented below.