Absorption of Co2 gas through Electro-Reduction of Molten salt for metal treatment proces

• Main Author: Nancy Julius Siambumn
• Format: Research Report
• Language: English
• Published: Universiti Malaysia Sabah 2014
• Subjects: TN Mining engineering. Metallurgy
• Online Access: https://eprints.ums.edu.my/id/eprint/22888/1/Absorption%20of%20Co2%20gas%20through%20Electro-Reduction%20of%20Molten%20salt%20for%20metal%20treatment.pdf; https://eprints.ums.edu.my/id/eprint/22888/

Molten salt carburisation process using electro-reduction of molten salts containing carbonate salt has been Investigated using CO2 as a continuous source of carbon. The effectiveness of electro-carburisation under various CO2 concentrations for mild steel sample and an attempt to electro-carburised stainless steel has also studied. The selection of molten salt mixture for electro-carburisation of mild steel and stainless steel was based on effective carburisation temperature, salt melting temperature and thermal stability. Mild steel was successfully electro-carburised at 800°C in two type of carbonate salt mixture (Na2CO)-NaCI and Li2CO)-K2CO)). Microstructural changes as revealed by optical were featured by the increase of the carbon rich cementite phase (Fe)C) at the expense of the original ferrite phase near the surface of the carburised samples. Microhardness profiles measured from the surface to the centre of the electro-carburised samples presented clear evidence of carbon penetration as a function of the electrolysis voltage, and the activity of carbonate Ions In the molten salts. The carbon-hardened case was up to 0.60 mm In thickness with hardness 1100HV In 60 minutes carburlsatlon at 800°C. Carburisation process is not possible at for stainless steel due to the formation of protective coating at high temperature, therefore usage of Na2CO)-NaCI and Li2CO)K2C0 3 were not suitable. Molten salt Li2CO)-Na2CO)-K2CO) that has melting temperature below 500°C was Identified suitable for stainless steel sample. No prominent case hardening obtained by stainless steel In 60 minutes carburisation under 500°C temperature, however microstructural changes revealed by optical microscope shows martensite structure presence and changed In size when cell voltage was varies. It Is suspected that electro-carburisation at more than 60 minutes Is required to make significant case hardening depth.