Effect Of Casting Pressure On Microstructure And Anti-abrasion Property Of Fe-Cr-C White Cast Iron

Liquid Die Forging technology for alloy casting can optimize the solidification structure and improve the mechanical properties by changing the solidification parameters.The wear resistance of Fe-Cr-C white cast iron is limited by the coarse and continuous carbides in the solidification structure,while the morphology and distribution of the carbides are related to the solidification parameters.The Fe-Cr-C white cast iron with hypoeutectic and eutectic composition was selected,and the sample was prepared by liquid die forging at the pressure of atmosphere to 170 MPa.The microstructure and the morphology of the samples were analyzed by optical microscope and scanning electron microscope?SEM?.The physical phase of the sample was characterized by X ray diffraction?XRD?,and the phase analysis and calibration were carried out by Jade software.Finally,hardness,toughness and impact wear properties of the specimens were tested.Comparison of solidification structure morphology,carbide phase evolution and related mechanical properties of Fe-Cr-C white cast iron under atmospheric and pressure.The solidification behavior of Fe-Cr-C white cast iron under pressure control mechanism of eutectic structure and carbide is established,and the following conclusions are obtained:?1?For the Fe-Cr-C white cast iron with hypoeutectic and near eutectic composition,the solidification structure is obviously refined than that of the atmosphere pressure.As the pressure increases,the distribution of each phase in the eutectic structure became more uniform.The solidification structure of the Fe-Cr-C white cast iron with hypoeutectic composition lath shape microstructure reduces,and equiaxed microstructure increases.The Fe-Cr-C white cast iron with near eutectic composition changed from lath shape to curved,short rod-like or polygon.?2?The effect of pressure on the microstructure of Fe-Cr-C white cast iron decreases with the increase of the cooling speed of the alloy.By comparing the microstructure of the alloy sampled at different positions,it is concluded that the pressure has little effect on the morphology?eutectic spacing,eutectic area,primary phase size?of the solidified microstructure,that is,the microstructure with high cooling speed near the mold.?3?Pressure can change the eutectic growth mode of the Fe-Cr-C white cast iron.Pressure changes austenite and carbide in eutectic structure from the parallel growth to the competitive growth,which is due to the change of the stability of solid-liquid interface during the eutectic solidification.Pressure changes the growth mode of the eutectic carbides of Fe-Cr-C white cast iron from faceted to non-faceted growth.?4?The nucleation rate and the content of the carbides in the Fe-Cr-C white cast iron increased significantly with the lifting of pressure.At the pressure of 160 MPa,the volume fraction of the carbide in the hypoeutectic alloy is 2 times that of the atmosphere pressure,and the content of the carbide in the near eutectic alloy increases by about 1.5times.?5?Increased solidification pressure can facilitate the transition of carbides to more stable types.The increase of solidification pressure can reduce the content of M₃C carbide and add the content of M₇C₃ carbide in the hypoeutectic alloys.The content of M₂₃C₆carbide in the near eutectic alloys decreases while the M₇C₃ increases.?6?When the casting pressure reaches about 160 MPa,the impact wear performance of the hypoeutectic alloy is 1.5 times higher than that of the atmosphere casting,and the near eutectic alloy is nearly doubled.Hardness of the both Fe-Cr-C white cast iron under the high-pressure casting has been obviously improved,but the impact toughness does not necessarily increase with the lifting of pressure.