Abstract
The effect of electric current pulse on the microstructure and corrosion resistance of hypereutectic high chromium cast iron was explored. The morphology of carbides in solidification microstructure was observed by an optical microscope and a scanning electron microscope and the composition was determined by an electron probe micro-analyzer. The microhardness of primary carbides and corrosion resistance of samples were also compared. Under the active of electric current pulse, the microstructure of hypereutectic high chromium cast iron was homogenized and its performance improved accordingly. On treatment by electric current, the morphology of primary carbides changed from thick long rods to hexagonal blocks or granular structures. The interlayer spacing of eutectic carbide decreased from ~26.3 μm to ~17.8 μm. Size statistics showed that the average diameter of primary carbide decreased from ~220 μm to ~60 μm. As a result, microhardness increased from 1412 HV to 1511 HV. No obvious microcrack propagation was found at the microindentation sites. The average length of microcracks decreased from ~20.7 μm to ~5.7 μm. Furthermore, corrosion resistance was remarkably enhanced. The average corrosion rate decreased from 2.65 mg/cm2·h to 1.74 mg/cm2·h after pulse current treatment.
Highlights
High Chromium Cast Iron (HCCI) containing 11~30 wt% chromium and 2.0~4.3 wt% carbon has been known as the best antifriction material in the world [1,2,3,4]
Due to its good wear resistance and corrosion resistance, HCCI is widely used in building, metallurgy, machinery, chemical industry and other fields [5,6,7,8]
Results is indicate thatwhich the microhardness andthan fracture primaryincarbide as. These results indicate that the microhardness and fracture toughness of primary carbide as well as the samples. These results indicate that the microhardness and fracture toughness of primary carbide as well as the compactness of matrix structure are improved after pulse current treatment
Summary
High Chromium Cast Iron (HCCI) containing 11~30 wt% chromium and 2.0~4.3 wt% carbon has been known as the best antifriction material in the world [1,2,3,4]. Due to its good wear resistance and corrosion resistance, HCCI is widely used in building, metallurgy, machinery, chemical industry and other fields [5,6,7,8]. With regard to the hypereutectic structure, it is usually supported by high content carbide, which has good wear resistance. If the morphology of carbides exhibits thick long-rod irregular shape, the toughness of HCCI will decrease, furtherly restricting its industrial application [11]. Based on the reported investigation, if the shape of primary M7 C3 carbide can be converted to fine blocks or granular structures, the wear resistance, corrosion resistance and toughness of HCCI will be comprehensively improved [3,4,10,12,13,14]
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