molybdenum on properties of gray cast iron

Figure 1 shows the graphite morphology of samples S1 ~ S4 in Table 1 observed under scanning electron microscope. According to EN ISO 945-1 2017 standard, it can be seen that the graphite type of all samples is type A. although molybdenum does not change the graphite type, the distribution and morphology of graphite have changed significantly.

It can be seen from Fig. 1 that the graphite of sample S1 (Mo 0.034%) is slender, and the graphite branching phenomenon is obvious. With the increase of molybdenum content, the graphite tends to become shorter and thicker, with fewer branches, and the graphite exists in an independent sheet form; The thickness of graphite sheet after molybdenum addition can be obviously seen in sample S3 (Mo 0.56%) and sample S4 (Mo 0.77%). In order to more accurately reflect the change of graphite length, 20 optical microscope photos were analyzed by image-j software( × All complete flake graphite in 100) shall be statistically analyzed.

As can be seen from Figure 2, the length of each sample is less than 100 μ The graphite proportion of M is more than 50%. However, with the increase of molybdenum content, the length of graphite becomes shorter, especially more than 300 μ The graphite proportion of M is greatly reduced, and the length of more than 300 can hardly be seen in samples S3 (Mo 0.56%) and S4 (Mo 0.77%) μ M graphite sheet, most of the graphite length is concentrated in 200 μ Below M. When graphite becomes shorter, its quantity increases accordingly.

Figure 3 shows the graphite quantity and its projected area fraction of samples with different molybdenum content. It can be seen that the graphite quantity per unit area increases significantly with the increase of molybdenum content, while the graphite area fraction decreases slightly, which shows that the average length of graphite sheet becomes shorter with the increase of molybdenum content.