Study On Microstructure Evolution And Performance Of Hypoeutectic High Chromium Cast Iron Under Pulsed Current

High chromium cast iron, which exhibited excellent wear resistance property, was widely used as a wear resistance material. In this paper, the microstructureand and performance of hypoeutectic high chromium cast iron were studied through electric current pulse treatment.During cooling solidification process of high chromium cast iron, the primary phase and eutectic structure all could be improved after the treatment of pulsating electric current for 3 min. Different pulse parameters had different effect on the primary phase and eutectic structure. Altought, the effect of elements content and distribution in solidification structure was not significance.This work also studied the effect of the pulse electric current parameters on the morphology of primary austenite, and found that the primary austenite was less relevant to the pulse electric current parameters. In addition, the microstructureof hypoeutectic high chromium cast iron was improved, and the primary phase of dendrite was obviously limited, grain size was refined and the microstructurehomogeneous was also improved after the different treatment time of electric current pulse. It was also found that the grain of the hypoeutectic high chromium cast iron was refined, and the length, thickness and space of flake eutectic carbide decreased. However, the phenomenon of coarseness would appear when the time of ECP was longer. From the change of solidification organization, the better result was obtained when the time of ECP treatment was 7min.While the nucleation and growth of primary austenite, the constitutional supercooling of cell growth front was decreased because of the electro-migration of pulse electric current and disturbance of the melt. The growth of primary austenite was restrained and the orientation growth of grain was eliminated, which could decrease the growth of austenite dendrites and secondary dendrite arms, thus the primary austenite morphologies was granular and spherical.During the insulation treatment process for 7 min without pulse electric current, the high temperature could benefit the dissolve of spheroidal austenite. However, many of spheroidal primary austenite formed after the pulse electric current treatment. The diffuse ability of intragranular atom and defect were enhanced, and the grain boundary of primary austenite was easier to move due to the thermal effect of the pulse electric current, thus promoted the dissolve of spheroidal austenite. When the temperature was 1280℃, the results found that primary austenite became fine particulate of uniform size and distribution.The impact toughness, micro hardness and impact abrasive wear resistance of the hypoeutectic high chromium cast iron was improved to some extent after the pulse electric current treatment, but anti-corrosion properties of alloys were changed little.