| Particle reinforced iron matrix surface composite is successfully fabricated by combining the methods of Self-propagating High-temperature Synthesis with casting. It not only remains the high toughness of the die steel matrix but also raises the hardness of the surface, thus improves the wear property of this material.Thermodynamical parameters of the Al-C-Ti system are calculated using the theory of solution thermodynamics. The result shows that TiC is the most stable phase and the content of Al should not be so high as to make iron brittle, usually lower than 40%. By calculating the adiabatic temperature and free enthalpy of Fe-C-Ti system, it shows that the content of Fe should be suitable at 30% and TiC is also the stable thermodynamical phase of Fe-C-Ti system. The reaction processes of the two systems are revealed by the DTA curve.The SHS products are observed by SEM and XRD. The results show that the Al-C-Ti system becomes easier to react as the grain size of Al, Ti become smaller and the content of Al grows. The Fe-Al-C-Ti system becomes easier to react as the size of Ti becomes smaller. Al can be used as diluent of Fe-C-Ti system to make the particle become smaller. As the initial temperature becomes higher, the two systems react more thoroughly. While preheating under 400 ℃ at atmosphere, the SHS reaction of the compact can also take place although it is somewhat oxidized. The SHS products after casting is also observed using SEM, XRD and EDS. The results show that the microstructure of the matrix is both mixed structure of martensite and pearlite. The grain size of the particle phase is round 1 μm and 2 μm and the particle of Fe-C-Ti system is smaller than that of Al-C-Ti system. The distribution of the particle phase is uniform, the matrix and the surface penetrate into each other. The surface of the steel matrix composites reinforced by Al-C-Ti system has more FeAl phase.The hardness of the surface composites increases dramatically except the surface about 0.5mm wide and gradually changes to the hardness of the matrix. The results of the ball-on-disk experiment show that its wear property improves obviously, about twice of the matrix. Its mechanism under normal temperature is adhesive wear and fatigue breaking-off. |
