Effect of Ti addition on morphology and size of primary M 7 C 3 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.