Study On Microstructure And Mechanical Properties Of TiC Particles Reinforced Steel Matrix Composites Prepared By Squeeze Casting

TiC steel-bonded cemented carbide has good performance and is widely used in various molds,cutting tools and wear-resistant tools.However,its preparation process is long and the price is high,and it generally needs secondary connection in application.In this paper,TiCp/steel matrix composites were prepared by squeeze casting method,supplemented by micro-powder activation process.It has the characteristics of low cost and short process flow,and can also realize the integration of composite materials and corresponding product preparation.Firstly,the effects of extrusion process parameters on the microstructure and properties of TiCp/steel matrix composites were studied.Then,the Mn13 with high toughness and the Cr8Mo2VSiwith high strength were used as the matrix,respectively.The effects of the volume fraction of TiCp,the type and amount of activated powder on the microstructure and mechanical properties（hardness,bending strength,impact toughness）of the composites were studied,which laid the foundation for the development of high-performance wear-resistant composites.The main results are as follows:（1）When the preform forming pressure is 20 MPa and the squeeze casting temperature is 1550°C,the ceramic particles in the microstructure of the prepared TiCp/steel matrix composites are evenly distributed,and there is no strip graphite produced by the high temperature decomposition of TiCp.However,when the volume fraction of TiCp in the composite is 65%,agglomeration occurs.The microstructure of different steel matrix in the composite is different.The microstructure of Mn13 is martensite and a small amount of austenite.The microstructure of Cr8Mo2VSimatrix is martensite,blocky M₇C₃carbide and banded M₂C and M₆C carbides.（2）For TiCp/Mn13 composites,with the increase of TiCp volume fraction（0%,35%,50%,65%）,the hardness of the composites increases gradually,and the hardness of the composites is more than 2 times higher than that of the matrix.The bending strength decreases gradually,and the maximum bending strength of 35%volume fraction composite sample is 439.0 MPa,but the increase of bending strength of 50%volume fraction composite sample is the largest.The impact toughness of the composites changes little.With the increase of Sipowder addition（0wt%,3.5wt%,7.5wt%）,the hardness of the composite increases gradually.The bending strength increases gradually,and the maximum bending strength of 7.5wt%Sipowder composite is 401.4MPa,and the increase of bending strength is also the largest.The change of impact toughness is small.With the increase of WC powder content（0 wt%,5.0 wt%,7.5 wt%）,the hardness of the composites increased gradually.The change of bending strength fluctuates greatly,but the increase of bending strength of 5.0 wt%WC powder composite is the largest.The impact toughness first increases and then decreases,and the impact toughness of 5.0wt%WC powder composite is the best at 3.5J/cm².（3）For TiCp/Cr8Mo2VSicomposites,with the increase of TiCp volume fraction,the hardness of the composites increases gradually.The bending strength decreases gradually,and the maximum bending strength of the 35%integral sample in the composite material is 642.7 MPa.The impact toughness changes little,and the maximum impact toughness of 50%volume fraction composites is 1.7 J/cm².With the increase of Sipowder content,the hardness of the composite increases gradually.The bending strength increases first and then decreases,and the maximum bending strength of 3.5wt%Sipowder composite is 308.7 MPa.The impact toughness of the composites changed little,and the maximum impact toughness of 0wt%Sipowder composites was 1.9 J/cm².With the increase of WC powder addition,the hardness of the composite increases gradually.The bending strength increases first and then decreases.When the addition amount of WC powder is 5.0wt%,the maximum bending strength is 375.2 MPa.The maximum impact toughness of 5.0wt%WC powder composites is 2.1J/cm².（4）Comparing the above two different matrix composites,it can be seen that the impact toughness of TiCp/Mn13 composites is generally higher than that of TiCp/Cr8Mo2VSicomposites.The hardness of the two composites is not much different,but the flexural strength of TiCp/Cr8Mo2VSicomposites is higher.（5）The flexural strength and impact toughness of TiCp/steel matrix composites prepared by squeeze casting are not high.The reason is that water glass is used as binder in ceramic preform,and glass phase is formed at the interface between TiCp and steel matrix.Because the glass phase is brittle,it will break first under external force,which reduces the mechanical properties of the composites.