Effect Of Silicon On Microstructure And Properties Of Sintered High Chromium Cast Iron

As a widely used wear-resistant material,high-chromium cast iron has the advantages of high strength and good wear resistance.The combination of the high volume fraction M₇C₃hard phase and the relatively tough iron matrix（usually austenite and martensite）is the main reason for the high wear resistance of high chromium cast iron.However,practical application shows that high chromium The main problem facing cast iron is still a good balance of hardness and toughness.The microstructure of ordinary cast high-chromium cast iron contains a lot of sharp chrysanthemum-like carbides,which actually plays a role in stress concentration,which makes the toughness worse.In order to improve the morphology of carbides,sintered high-chromium cast iron is prepared by powder metallurgy,and the growth of carbides inside can reach an ideal state.The high-silicon scrap iron used to prepare high-chromium cast iron is cheap and widely available.At the same time,silicon plays a non-negligible role in the preparation of high-chromium cast iron.The silicon content is often strictly limited to the range of 0.6～1.0%.The obvious improvement of carbide morphology and distribution in the structure of sintered high-chromium cast iron reduces the sensitivity of the matrix to the toughness of high-chromium cast iron,which may expand the control range of silicon content in high-chromium cast iron.In this paper,sintered high-chromium cast iron with silicon content ranging from0.15～3.23%was prepared by super solid phase liquid phase sintering,and the corresponding best performance was obtained by adjusting the sintering temperature.The metallographic microscope,scanning electron microscope,X-ray diffractometer and other equipment were used to analyze the structure of the material.The mechanical properties of the material were tested by means of hardness,flexural strength,impact toughness,etc.,and the impact grinding of the material was studied.Grain wear performance.The main findings are as follows:Firstly,silicon can increase the amount of liquid phase during sintering,reduce the viscosity of the liquid phase,increase the liquidity of the liquid phase,and promote the densification of sintered high-chromium cast iron.At the same time,when silicon is added,the sintered high-chromium cast iron can begin to densify at a lower temperature.Lower the temperature to near full densification and expand the effective sintering temperature range.Secondly,the matrix in sintered high-chromium cast iron with a silicon content ranging from 0.15～3.23%is a mixed structure of martensite/ferrite and residual austenite,and the carbide is M₇C₃type carbide.Since si is basically solid-dissolved in the matrix,the solubility of C and Cr in the matrix is reduced,the degree of right shift of the C curve and the stability of austenite are reduced,and then the matrix structure is changed.When the silicon content is2.36～3.23%,a part of pearlite exists in the matrix.When the silicon content is 0.15～1.48%,it can refine the carbide and reduce the volume fraction of carbide.Once it exceeds 1.48%,the carbide will grow again and the volume fraction of carbide will increase.At the same time,when the silicon content reaches 3.23%,the carbide morphology is deteriorated,which further damages the mechanical properties.In the sintered high chromium cast iron with a silicon content ranging from 0.15～3.23%,the sintered high chromium cast iron has the best comprehensive mechanical properties at a sintering temperature of 1230^oC when the silicon content is 1.48%.At this time,the hardness is 55.5HRC and the impact toughness is 9.59J/cm²,2208.9MPa bending strength.It can be seen that the silicon content of sintered high-chromium cast iron can reach 1.48%.However,when the silicon content exceeds 2.36%,the strength and toughness are significantly reduced.Finally,sintered high-chromium cast iron with a silicon content ranging from0.15～3.23%has good wear resistance under low impact energy conditions,and the wear mechanism is mainly brittle fracture.Under medium and high impact energy conditions,when the silicon content is 0.15～1.48%compared to 2.36～3.23%,the wear resistance is significantly better.The former’s main wear mechanism is still brittle fracture,but the latter’s main wear mechanism is fatigue spalling.