Study on the kinetics of the growth of intermetallic layer on the surface of CK45 steel during hot dipping process in molten aluminium

Abstract

Aluminizing is one of the processes that increases the resistance to corrosion and oxidation of the steels at high temperatures. During this process, the intermetallic compounds that formed on the steel surface, causes desirable properties. Among the various methods of aluminizing, hot dipping is more economical and feasible. In this work, aluminizing of CK45 steel was carried out via hot dipping process at three immersion temperatures of 730 °C, 770 °C and 830 °C and for different immersion times in molten pure aluminium. By using EDS analysis, the phase formed on the surface of steel was detected as Fe2Al5. The thickness of this phase was measured by optical microscope for the different temperatures and times. The plots of intermetallic layer thickness versus the square root of time indicated a linear behaviour that means the growth of this intermetallic layer obeys the diffiusion-controlled kinetics. By plotting the graph of logarithm of slops as a function of reciprocal temperature, the activation energy of the growth of the Fe2Al5 was calculated as 121 kJ/mol.