Evaluation of friction conditions in powder compaction for admixed and die wall lubrication

Abstract

For the purpose of modelling powder compaction, a quantitative evaluation of the friction conditions at the die wall interface is required. Using an instrumented compaction die, the friction at the interface between powder compact and die wall was evaluated through an empirical parameter called the slide coefficient, obtained from the applied pressure/transmitted pressure ratio. For powder compaction modelling, knowledge of the friction coefficient at the interface, however, is much more useful but its measurement is difficult in real experimental conditions. A procedure based on the evaluation of the radial stress/axial stress ratio leads to the quantitative determination of the friction coefficient in admixed zinc stearate added to iron powder with and without die wall lubrication. The resulting decreasing friction coefficient at the end of compaction gives a more uniform density characterised by low loss of pressure 1 Variables associated with single action pressing from through the compact and lower ejection energy per upper punch: angle w characterises radial stress/axial unit volume of the compact.PM/0826 stress ratio Professor Turenne and Ms Gode `re are in the De ´partement de ge ´nie physique et de ge ´nie des mate ´r-and ejection of the green part from the die but are difficult to remove during sintering. Moreover, the importance of iaux, E ´cole Polytechnique de Montre ´al, C.P. 6079, Succ. Centre-Ville, Montre ´al, PQ, H3C 3A7, Canada, the influence of lubricant content in powder mixes on mechanical properties of green and sintered parts is and Dr Thomas and Mr Mongeon are at the Industrial Materials Institute, National Research recognised.3 Some technical approaches have been published to suggest die wall lubrication but the economic Council

Deformation behaviour of aluminium low-micron MMCs and MMNCs at warm working temperatures (0.3-0.5 Tm)

“…The frictional force opposes the applied force and decreases the amount of pressure transmitted to the powder for consolidation (Turenne et al, 1999), so high pressures result in high green densities (Tiwari, Rajput and Srivastava 2012). Thus the lower densification observed at the core of the sample (Figure 8b) is an indication of a non-uniform density distribution in the sample.…”

Lubricant Influence on the Ejection and Roughness of In-Die Electro Sinter Forged Ti-Discs

“…Two different lubrication methods are described in literature, namely admixed and die-wall lubrication [5]. In admixed lubrication, the powder is mixed with the lubricant, while the die-wall lubrication is based on the application of the lubricant directly on the die-wall.…”

“…A number of factors influence the friction, e.g. lubrication, compaction pressure, roughness of the tools and friction between particles [5]. The compaction pressure generates a radial pressure on the die-wall during the process.…”

Effect of Lubrication on the Improvement of Uniformity in Uniaxial Powder Compaction

“…The weight Table 1 Experimental condition for the estimation of the axial density distribution of powder is 42.0 g + lubricant amount g, and as a result density ratio ρ which is defined as the ratio of the compact density to materials density becomes ρ = 0.85. The density of each lubricant is 1.14 g/cm 3 in case of StZn, and is 0.8 g/cm 3 in case of Wax. Hence the critical amount of each lubricant becomes 2.55 wt.% in case of StZn, and becomes 1.76 wt.% in case of Wax.…”