Effect of molybdenum on carbide precipitation in experimental samples of gray cast iron

Fig. 1 shows the scanning electron microscope BSE photos of gray cast iron samples with different molybdenum content. It can be seen from Fig. 1 that no carbide precipitation is observed in the reference gray cast iron sample S1 (0.034% Mo); With the increase of molybdenum content in gray cast iron samples, a small amount of carbide precipitation (29) began to occur in S2 (0.26% Mo) · Mm-2), the number of S3 (0.56% Mo) and S4 (0.77% Mo) carbides further increased to 145 respectively · Mm-2, 203 · Mm-2, the size is also increased. In addition, it can be seen from the figure that carbides are distributed in the matrix in rod, strip and other irregular shapes.

(a) Sample S1; (b) Sample S2; (c) Sample S3; (d) Sample S4

Fig. 2 is the SEM diagram of typical gray cast iron carbides partially enlarged and the corresponding EDS energy spectrum analysis. The gray cast iron carbides are distributed in the interior of pearlite clusters and at the boundary of pearlite clusters in the form of long strips or rods, and the pearlite sheets on both sides of gray cast iron carbides have different orientations.