Elimination of the Lubricant in Metal Powder Compacts

摘要

P/M lubricants (zinc stearate, EZ and ethylene-bis-stearamide, EBS) and their admixes, were studied by thermogravimetric analysis (TGA) and differential scanning calorimetric (DSC) techniques. The effect of heating rate, type of presintering atmosphere and temperature were evaluated. Additionally, the lubricant elimination from iron-based compacts containing 1.5% in weight of EBS was studied as a function of compaction density. The obtained results from DSC measurements, allows to propose the type of reactions that take place during the burnt-off step, for each one of lubricants tested at different atmosphere conditions. The obtained results from thermogravimetric analysis, show that the best lubricants are those that have the high levels of EBS. Also, it was observed that lubricants elimination decreases when heating rate is increased and that longer times are equired for it. When an oxidant atmosphere is present, the decomposition is promoted for EZ, it does not offer benefits in the decomposition of EBS. Lubricant elimination process was not improved when a wet argon atmosphere was used in the range of temperature and concentration studied in the present work. On the other hand, lubricant elimination behavior from iron-based compacts was different from that shown by pure lubricant samples. Compact density affects lubricant elimination; lubricant elimination is more difficult when the compact density is increased. In order to eliminate lubricants from the iron-based compacts, it is necessary to use different temperature, time and atmosphere conditions.