A Investingation Of45Steel And Aluminum Surface Coated By M_n+1AX_n Ternary Lamellar Compound

Ti3SiC2and Ti3AlC2are a new type of ternary lamellar compound which combine theproperties of both ceramics and metals. It is worth noting that Ti3SiC2and Ti3AlC2possessa graphite-like lamellar structure which has both high mechanical strength and excellentcorrosion resistance and self-lubrication. Therefore, Ti3SiC2and Ti3AlC2coatings play asignificant role in protecting and improving the self-lubrication of the metal matrix.High activity Ti-Si-C powder system was first obtained through ball-milling method,followed by cold press process, and then was placed on the Al plate. Ti3SiC2-Al compositewas prepared by laser ignition and plasma ignition approaches. The Ti-Al-C powdersystem, produced by ball-milling method, together with Fe matrix was put into thegraphite mould. Ti3AlC2-Fe composites then were manufactured by using spark plasmasintering (SPS).The microstructures and compositions of the as-prepared products were examined bymeans of XRD, SEM and EDS. The coating mechanism of self-propagating combustion athigh temperature was analyzed. The relationship between the thickness of Al matrix andthe heat release of the Ti-Si-C powder ignited by SPS was interpreted particularly. Theconnection mechanism of Ti-Al-C and45steel was also presented.Results show that the metallurgical metal-ceramic bonding was formed due to thelarge amount of heat released during the self-propagating combustion process. Thereaction products were Ti3SiC2, Ti5Si3and TiC, respectively. Al diffused to the Ti-Si-Ccoating while C to Al matrix diffusion was also revealed. It can be found that extra liquidAl restrained the formation of Ti3SiC2in the Ti-Si-C self-propagation system. Themetallurgical binding between Ti-Si-C and Al matrix was realized due to the appropriateliquid Al. High-purity Ti3AlC2can be prepared under the preparation temperatures of1100oC and1200oC during the SPS process. At the same time, the connection between Ti3AlC2and45steel matrix was formed. However, the composite microstructure deteriorated asthe steel matrix was melted at1080oC. Hence, the reduction of the sintering temperatureby extending the ball-milling time was studied. The results show that, after12h ball-milling process, high-purity Ti3AlC2coating was obtained on the steel surface at1000oC sintering. Reaction boding between steel matrix and Ti3AlC2was formed and largeamount of TiC existed in the transition area. As a result of the large difference between thethermal expansion coefficients of metal and ceramic and its brittleness, the fracture of thetransition area happened during the cooling process and cracks were generated. The finaltransition zone of45steel and Ti3AlC2was Fe/TiC/Ti3AlC2.