In Situ Synthesis Of (Ti, W)C Reinforced Steel & Iron Matrix Composites And Their Microstructure And Properties

In the present work, the (Ti,W)Cp/Fe composites in which Ti was substituted by W were prepared by using in situ synthesis techniques, and the effects of chemical compositions and casting processes on microstructures and mechanical properties of this new composite were investigated. The results show that production of in situ (Ti,W)Cp/Fe composites is available through alloying TiC by W. Also, the casting techniques and compositions of alloy have great influence on the formation and morphologies of the (Ti,W)C phase. It is showed that (Ti,W)C phase, as the only one second phase, can stably exist in ferror matrix as the ratio of Ti and W is higher than 4/6, the morphology of (Ti,W)C is equiaxed particulate as Ti/W equals 1. It is feasible to synthesize in situ TiC/Fe and (Ti,W)C/Fe composite with inexpensive and abundant raw materials including pig iron, Ferrotitanium and Ferrotungsten by the reactive casting technique in an inductive electronic furnace. In the composites, the TiC and (Ti,W)C mainly exhibit two kinds of morphologies, spherulic and rod-like ones. Analysis shows that the spherulic TiC and (Ti,W)C are proeutectic phase in the melt, while rod-like one is eutectic phase during solidification of the melt. It is found that the casting process parameters such as reaction temperature, melting time and the followed solidification rate greatly influence the microstructure of the composites. There appears lots of unexpected Fe2Ti and Fe3C along the boundary of crystalline in the composites when the melting temperature is less 1600℃, reactive time shorter than 15min and the solidification rate is lower relatively. Properly increasing the cooling rate of the melt is good for prevention of Fe2Ti and Fe3C formation during the solidification. The ideal process parameters under this investigation is that melting temperature, reactive time and casting method are 1650℃, 15min and iron mold casting. Mechanical tests prove that the Fe2Ti and Fe3C formed during solidifying are beneficial to improvement of the hardness but harmful to impact toughness of the composites. Impact fractographic analysis shows that cracks usually originate and then propagate from them . The much...