Study of compaction and ejection of hydrided-dehydrided titanium powder

Abstract

Three similar varieties of pure Ti hydride-dehydried (HDH) powders were tested for the understanding of the variables that have an influence on the compaction process of Ti powders. The study shows that small differences in the characteristics of the powders lead to very different behaviours in the compaction stage. Compressibility curves, friction with the die walls and ejection forces are discussed in this study. The results are compared with a commercial iron powder as a reference to complete the discussion, as well as to show the enhancements and modifications that should be performed in Ti powders to design an optimized powder suitable for being pressed in an industrial process.

Analysis of the Cold Compaction Behavior of Titanium Powders: A Comprehensive Inter-model Comparison Study of Compaction Equations

“…[27] Eventually, according to Bockstiegel, [28] the interest shifted more towards an analytical problem-finding a simple but adequate mathematical description for experimentally observed compaction curves. [1,2,[6][7][8][9][10][11][12][13][14] The compaction curves for ITP-produced Ti, [12] CSIR-produced Ti, [8] Ho¨gana¨s AB produced Ti and TiH 2 , [13,17] Armstrong produced Ti and Ti-6Al-4V, [14,17] spray-dried powders, [20] for example, have also been reported Comparing the compressibility of different powder CP-Ti, sponge, HDH, and various Ti-6Al-4V powder mixtures (up to 1200 MPa) several researchers, see Refs. 1, 2, 6 through 9, 11 through 13, and 17 for example, have also studied and compared the compaction behavior of different Ti powder.…”

“…[4,5] Several studies in literature have established relationships between the compaction pressure, the powder characteristics (such as impurity levels and particle size shape), different compaction route (cold, hot, or dynamic compaction), and the obtained properties of the compacts (density, sinterability and strength) with varying degrees of success. [1,2,[6][7][8][9][10][11][12][13][14][15][16][17][18] Studies into the cold compaction of titanium and titanium-based powder materials are necessitated by fact that titanium PM also offers improved chemical homogeneity and refined microstructures [2] in addition to a cost and energy-consumption reduction benefit-given the high cost of titanium powder material. In addition, challenges associated with titanium powder compaction such as (i) the obvious high reactivity of titanium powder material in air, (ii) its inherent difficulty to press into green bodies due to its high hardness and inductile properties, [13] (iii) problems associated with compact cold welding to the die wall [9,11,13,14,19] as well as (iv) the high ejection force required.…”

“…In addition, challenges associated with titanium powder compaction such as (i) the obvious high reactivity of titanium powder material in air, (ii) its inherent difficulty to press into green bodies due to its high hardness and inductile properties, [13] (iii) problems associated with compact cold welding to the die wall [9,11,13,14,19] as well as (iv) the high ejection force required. [9,11,13] These challenges, for example, further justify the continued interests in the cold compaction behavior of titanium powders.…”

“…Some noteworthy findings from literature are summarized in Table I. According to Table I, many research articles have reported on the compressibility behavior of titanium powders [1,2,[6][7][8][9][10][11][12][13][14]17,20,22,25] ; evidently, only a very few have paid particular attention to the analysis of the cold compaction behavior of titanium powders using existing or new compaction equations, see References 10,12,14,22, and 25 for example. Those that have, for unspecified reasons, have selectively applied only a few models.…”

Colloidal approach for the design of Ti powders sinterable at low temperature

“…It is remarkable that the most of the work currently done in processing of Ti powders by cold pressing is carried out using irregularly-shaped powders [16], as spherical powders can only be pressed by more advanced processing, as hot pressing, hot isostatic pressing or powder injection molding. Results in this work demonstrate that spherical powders can be successfully processed by cold pressing through granules shaped in a previous colloidal step, achieving green density values even higher than those obtained by coarser and irregular-shaped powders [3, 16,17]. It is worth mentioning that Ti10 powders before granulation could not be pressed in the uniaxial press, due to the small size and spherical shape of particles, and also Ti45 powders could not be granulated as it was not possible to produce stable suspensions due to the big particle size.…”