Accelerated Carbon Atoms Diffusion in Bearing Steel Using Electropulsing to Reduce Spheroidization Processing Time and Improve Microstructure Uniformity

Herein, the thermodynamic and kinetic limitations of carbide dissolution behavior during the traditional heat treatment process are broken through the external field treatment. The difference in electrical conductivity between the matrix and the carbide affects the electric current distribution, which ultimately results in electric field distortion. The numerical calculation results show that under the coupled field of heat and pulsed electric current, the distribution of the current density around the particles is related to the size of the particles. The selective distribution of current caused the energy difference to eventually promote the preferential dissolution of coarse network carbides at grain boundaries. The redistribution of carbon atoms between the grain boundaries and the grain interior provides a good initial structure for the subsequent precipitation process, and finally, uniform precipitation of cementite is achieved in the matrix. Meanwhile, the electromigration of carbon atoms under pulsed electric current increases the diffusion rate of carbon atom and shortens the processing time (traditional heat treatment is about 20 h, and the electropulse-based method in this study is about 4 h).