Effect of electric current pulse on size of primary carbides in hypereutectic high chromium cast irons in different solidification stages

2019 ◽  
Vol 6 (12) ◽  
pp. 126551 ◽  
Author(s):  
Baoyu Geng ◽  
Rongfeng Zhou ◽  
Yongkun Li ◽  
Yehua Jiang
Keyword(s):  
Electric Current ◽  
Current Pulse ◽  
Electric Current Pulse ◽  
Cast Irons ◽  
High Chromium ◽  
Primary Carbides

scholarly journals Effect of Electric Current Pulse on Microstructure and Corrosion Resistance of Hypereutectic High Chromium Cast Iron

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2220 ◽  
Author(s):  
Haiyang Lv ◽  
Rongfeng Zhou ◽  
Lu Li ◽  
Haitao Ni ◽  
Jiang Zhu ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Cast Iron ◽  
Electric Current ◽  
Current Pulse ◽  
Electric Current Pulse ◽  
High Chromium ◽  
High Chromium Cast Iron ◽  
Microcrack Propagation ◽  
Primary Carbides ◽  
Chromium Cast Iron

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.

scholarly journals Change in Primary (Cr, Fe)7C3 Carbides Induced by Electric Current Pulse Modification of Hypereutectic High Chromium Cast Iron Melt

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 32 ◽  
Author(s):  
Baoyu Geng ◽  
Rongfeng Zhou ◽  
Lu Li ◽  
Haiyang Lv ◽  
Yongkun Li ◽  
...  
Keyword(s):  
Cast Iron ◽  
Electric Current ◽  
Current Pulse ◽  
Defect Density ◽  
Micro Hardness ◽  
Electric Current Pulse ◽  
High Chromium ◽  
High Chromium Cast Iron ◽  
Primary Carbides ◽  
Chromium Cast Iron

In this work, an electric current pulse (ECP) of 500A was applied on a hypereutectic high chromium cast iron (HHCCI) melt before it began to solidify, and the effect of ECP on primary carbides was investigated. The characteristics of the primary carbides were analyzed by X-ray diffraction (XRD), electron probe micro-analyzer (EPMA), transmission electron microscopy (TEM), micro hardness tester, and other techniques. The results showed that ECP not only refined the primary (Cr, Fe)7C3 carbides, but also decreased the average content of Cr in the primary carbides. At the same time, the average value of micro hardness of the primary carbides increased by about 84 Kgf/mm2, which contradicts existing knowledge that hardness increases with an increase in Cr content. XRD analysis showed that the crystal structure of the primary carbides did not change. The results of EPMA indicated that the Cr/Fe ratio gradually decreased from the center to the edges of the carbide particles. Further investigation revealed that the uneven distribution of elements caused by ECP led to an increase in defects (including twins, antiphase boundaries, and dislocations). This increase in defect density is the main reason for the increase in micro hardness instead of the expected decrease. The mechanism of the change in primary carbides was analyzed in detail in this paper, which has provided a new method for the refinement of primary carbides and for improving the properties of primary carbides.

Effect of Electric Current Pulse on Carbide in Hypereutectic High Chromium Cast Iron

2012 ◽  
Vol 457-458 ◽  
pp. 174-180 ◽  
Author(s):  
Hua Chen ◽  
Rong Feng Zhou ◽  
Ye Hua Jiang ◽  
Rong Zhou
Keyword(s):  
Cast Iron ◽  
Electric Current ◽  
Current Pulse ◽  
Processing Time ◽  
Hard Phase ◽  
Electric Current Pulse ◽  
High Chromium ◽  
High Chromium Cast Iron ◽  
Primary Carbides ◽  
Chromium Cast Iron

It has significant engineering practicability that refining the carbides as hard phase in hypereutectic high chromium cast iron. The high chromium cast iron samples during the course of solidification were treated with electric current pulse (ECP) from the temperature of 1350 °C and 1360 °C. The effects of ECP treatment of starting temperature, processing time on the shape, size, and distribution of primary carbides was investigated. The mechanism of primary carbides refined by ECP process was also analyzed preliminarily.

Microstructure Refinement of Hypereutectic High Chromium Cast Iron with Electric Current Pulse

2013 ◽  
Vol 690-693 ◽  
pp. 147-152 ◽  
Author(s):  
Hua Chen ◽  
Ling Zhang ◽  
Sheng Ming Wang
Keyword(s):  
Cast Iron ◽  
Electric Current ◽  
Current Pulse ◽  
Pulse Frequency ◽  
Solidification Structure ◽  
Electric Current Pulse ◽  
Electric Voltage ◽  
High Chromium ◽  
High Chromium Cast Iron ◽  
Chromium Cast Iron

The effect of electric current pulse (ECP) on the solidification structure of hypereutectic high chromium cast iron was studied. The orthogonal array L9 was used to determine the effect of three process parameters of ECP, which were electric voltage, pulse frequency, pulse width. According to the experimental results, the solidification structure of hypereutectic high chromium cast iron was modified from large grains to finer grains with equiaxed crystals, by allowing the ECP to act on liquid.

Refinement of inclusions in molten steel by electric current pulse

2015 ◽  
Vol 31 (13) ◽  
pp. 1555-1559 ◽  
Author(s):  
W. B. Dai ◽  
J. K. Yu ◽  
C. M. Du ◽  
L. Zhang ◽  
X. L. Wang
Keyword(s):  
Electric Current ◽  
Current Pulse ◽  
Molten Steel ◽  
Electric Current Pulse

Electric Current Pulse Welding of Titanium with 18-10 Stainless Steel

2009 ◽  
Vol 83-86 ◽  
pp. 1251-1253 ◽  
Author(s):  
E.G. Grigoryev ◽  
V.N. Bazanov
Keyword(s):  
Stainless Steel ◽  
Electric Current ◽  
Current Pulse ◽  
Contact Zone ◽  
Welded Joints ◽  
High Speed ◽  
Welded Joint ◽  
Electric Current Pulse ◽  
Pulse Effect ◽  
Different Thickness

The purpose of the work was to determine the capabilities of the pulse effect of electric current and pressure to produce welded joints of various component parts of different thickness from 18-10 stainless steel and titanium. Application of electric current pulses on the surfaces of contacting metallic conductors leads to considerable changes in the surface structure. Depending on the initial state of the surfaces and parameters of the pulse effect this can result in melting without formation of joints, formation of a strong welded joint with characteristics no worse than those of welded metals, and in destruction of the contact zone. A combination of a short electric pulse with simultaneous application of mechanical pressure in the weld zone causes high-speed deformation of the contact zone. The process of joint formation itself does not cause any appreciable diffusion during welding. The greatest energy emission and the maximal heating occur on the contacting surfaces being welded with the passage of an electric current pulse through the welding zone. Simultaneously with intensive heating, and due to applied pressure, high-speed deformation of materials takes place and a strong welded joint is formed. Optimal parameters for the welding of titanium and 18-10 stainless steel have been determined on the basis of the tests conducted. Investigations into the welding of titanium and 18-10 stainless steel have shown that application of a short electric current pulse and pressure produces stronger welded joints composed of both similar and different metals of considerably different thickness.

scholarly journals Effect of High Density Electric Current Pulse on Solidification of Cu-37.4 wt.%Pb Monotectic Alloy Melt

2019 ◽  
Vol 26 (1) ◽  
pp. 34-40
Author(s):  
Teng MA ◽  
Guihong GENG ◽  
Xiaosi SUN ◽  
Xi HAO ◽  
Weixin HAO
Keyword(s):  
Wear Resistance ◽  
Electric Current ◽  
Current Pulse ◽  
Metal Cluster ◽  
High Density ◽  
Formation Mechanisms ◽  
Electric Current Pulse ◽  
Monotectic Alloy ◽  
Scanning Calorimetry ◽  
Cluster Theory

The effect of high-density electric current pulse (ECP) on the solidification of Cu-37.4 wt.%Pb monotectic alloy melt was investigated. The microstructure formation mechanisms of ECP were clarified according to liquid metal cluster theory. The results demonstrated that with ECP treatment, the microstructure of Cu-Pb monotectic alloy became finer, the distribution of Pb phase in the matrix was more even and the solute trapping was significantly apparent. Based on the metal liquid cluster theory under ECP, the solid solubility increase result might be due to the salvation clusters increase under the action of pulse current, leading to the binding force increase among solute atoms and solvent atoms. Simultaneously, the aforementioned results were verified through the Differential Scanning Calorimetry (DSC) curve analysis. The results of hardness test, anti-friction test and wear- resistance test show that the ECP can enhance the hardness, improve the properties of anti-friction and wear-resistance of the alloy.

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