Document Type thesis Author Name Saha, Deepak URN etd-10014-233109 Title De-lubrication during sintering of P/M compacts: Operative mechanism and process control strategy Degree MS Department Materials Science & Engineering Advisors Prof. Diran Apelian, Advisor Prof. Richard Sisson Jr., Department Head Keywords delubrication powder metallurgy lubricant pyrolysis sintering De-lubrication Date of Presentation/Defense 2000-12-12 Availability unrestricted
De-lubrication is the first stage in a sintering operation, where the lubricants (higher weight hydrocarbons) are removed from the parts by controlled heating. Improper de-lubrication leads to defects such as blistering, sooting, micro-porosity etc in a sintered part. Most of these problems arise, as there exists a gap in the present understanding of de-lubrication. The primary motive of this work is to direct research towards the development of sensors and controls and thus, mitigate the various problems due to improper de-lubrication. Currently, there exists a myriad of lubricants being used during the process of compaction. They include metallic based lubricants, polymers and non-metallic lubricants. In this work, research was limited in understanding the de-lubrication of EBS (Ethylene Bisstearimide), as, it the most commonly used lubricant in the industry. It has replaced commonly used lubricant due to cleaner burnouts, absence of metallic residue and, cost effectiveness. The entire work is divided into three phases:
• Phase 1: Ascertained the most important parameters that affect the kinetics of de-lubrication.
• Phase 2: Investigated the type of gases released during the decomposition of EBS.
• Phase 3: Recommended a control strategy.
TGA (Thermo-gravimetric analysis) was used in the phase I, the results clearly show that the rate of heating is the most important parameter during de-lubrication. Identification of gases was performed using the FTIR (Fourier transform infrared spectroscopy) and DUV (Deep ultraviolet spectroscopy). This constituted the second phase of our experiments. The primary gases identified in Phase II were carbon dioxide and a hydrocarbon (hepta-decane). Finally, an empirical model for de-lubrication has been proposed in Phase III. The model was verified in an industrial furnace. It has been observed that there exists a very good correlation between the proposed empirical model and the experiments performed in Phase II of this study.
This study lays down the following guidelines for the development of future sensors and controls:
• The development of future sensors should focus in the detection of CO2 and hepta-decane.
• Rate of heating determines how fast or slow the lubricant decomposes and finally escapes form the compacted part.
• The empirical model may be used, as a means to determine the time a part should reside in a furnace for complete lubricant burnout at a given heating rate.
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