Effect Of Pulse Current Treatment On Distribution And Properties Of Hypereutectic High Chromium Cast Iron

Hypereutectic high chromium cast iron (HHCCI) has been widely used under the circumstance of high wear-resistant for a long time due to its higher hardness and wear-resistant of primary carbide and lower production costs. With the increasing of carbides amount, the wear-resistant of HHCCI can be improved. However, the large size of the primary carbides will increase the brittleness. Meanwhile, the mechanical mixture of eutectic carbides and matrix constituent will be a supporting for the primary carbides. And the morphological distribution of eutectic carbides has an influence on the fragmentation degree of matrix which will affect the mechanical property. In this paper, the electric current pulse (ECP) was used to treat with the HHCCI during the solidification process. The effect of ECP treatment on the microstructure element distribute and properties was investigated.The tubular resistance furnace was employed to control the HHCCI temperature. The appropriate remelt temperature was chosen to study the effects of ECP treatment time on the water-cooled microstructure. The results showed that the water-cooled microstructure of sample obtained the best morphology at 1380℃. When the ECP treatment time was less than 3 minutes, the equivalent diameter of primary carbides in water-cooled microstructure was reduced with the increase of the treatment time. When the ECP treatment time reached 3 minutes, the primary carbides were refined significantly. However, as the ECP treatment was more than 3 minutes, the microstructure became worse. On the basis of the above test, the EDS line scanning and EPMA were used to analyze the effect of ECP treatment on the element distribution of microstructure. The results showed that ECP treatment could promote the migration of atoms in the melt and reduce the content of Cr element in primary carbides.In 3.5% NaCl solution, the results showed that the corrosion potential of HHCCI sample was improved and the corrosion current density was improved by applying ECP treatment. However, the ECP treatment had little effect on the corrosion potential when the pulse width was between 10 μs and 50μs. Besides, when the pulse width reached 100 us, the rod shape primary carbides and eutectic carbides increased significantly, while the corrosion potential became lower.The results showed that the microstructure of HHCCI slab was refined after the ECP treatment. The refine level and mechanical property of the microstructure were enhanced with the increase of ECP treatment time. When the ECP treatment time reached 5 minutes, the tensile strength and impact toughness reached the peak value. The values were 203.2 MPa and 2.750 J/cm2, respectively. The values of the tensile strength and impact toughness were improved by 70% and 24% when compared with the HHCCI slab without ECP treatment.