Xiaohui Zhi

Effect of Ti addition on morphology and size of primary M7C3 type carbide in hypereutectic high chromium cast iron

Abstract Effect of Ti addition on the morphology and size of primary M7C3 type carbide in hypereutectic high chromium cast iron was investigated. The results indicated that the carbide is refined gradually, and its morphology becomes more equiaxed as titanium addition increases, but rather slowly when Ti addition exceeds 0·95%. The qualitative measurement result indicated that value shape factor K increases clearly first and then changes little, and the average equivalent diameter D changes against K exactly. Furthermore, by TEM analysis and Brammit’s theory calculation, the results also indicated that there are orientation relationships of TiC||M7C3 and [011]TiC||[0001]M7C3 between M7C3 type carbide and TiC, and the lattice misfit δ between TiC and M7C3 is 1·32%, explaining that TiC may provide the effective substrate plane for M7C3 nucleation to ameliorate morphology and size of primary M7C3 type carbide.

Effect of titanium on the as-cast microstructure and impact toughness of hypereutectic high-chromium cast iron

Abstract The effect of titanium on the as-cast microstructure of a hypereutectic high-chromium cast iron was investigated by means of optical microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results indicate that the primary M7C3 carbides are refined and spheroidized with the addition of a suitable amount of titanium. TiC is found in the primary carbide by energy dispersive spectroscopy analysis. The mechanism of titanium modification on the microstructure of the alloy is also discussed. In addition, the impact test result indicates that, compared with the hypereutectic high-chromium cast iron without titanium addition, the impact toughness value of hypereutectic high-chromium cast iron with titanium additions is improved and approximately reaches 6.4 J · cm−2.