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

• Published in: Steel research international Vol. 91; no. 7
• Main Authors: Hao, Jianqiao, Zhang, Hexiong, Zhang, Xinfang, Liu, Chengbao
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.07.2020
• Subjects: Atoms & subatomic particles; bearing steel; Bearing steels; Carbides; Carbon; carbon atom diffusion; Cementite; Current distribution; Diffusion rate; Dissolution; dissolution of cementite; Electric currents; Electric fields; Electrical resistivity; Electromigration; Grain boundaries; Heat treatment; pulsed electric current; Spheroidizing; spheroidizing annealing
• ISSN: 1611-3683; 1869-344X
• DOI: 10.1002/srin.202000041

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). The effect of pulsed current on spheroidizing annealing of 1C–1.5Cr bearing steel is studied. The results show that electric pulse accelerates the diffusion of carbon atoms in the bearing steel to reduce the time of the spheroidization process and improve the microstructure uniformity.