The unit area gain of high nickel ductile iron at 900 C for different working hours is recorded in Figure 1. It can be seen from Figure 1 that the unit area gain increases with the working time.At first, the growth rate was slow, mainly due to the loss of graphite and the dual action of oxidation of iron and silicon, and then through the rapid growth stage, the formation of SiO2 and Cr2O3 double oxide films gradually took place. When the thickness of oxide films reached a certain value, the oxidation rate increased with the increase of working time, but the growth rate slowed down.Fit the curve after fitting as shown in Figure 2a and follow the rule of Formula 1. In order to eliminate the error in the earlier stage, the curve of stable growth stage is fitted as shown in Figure 2B and the rule of Formula 2 is followed.
The thickness change of the oxide scale under different working hours at 900 C during the experiment is shown in Figure 3. It can be seen from the figure that the thickness of the oxide scale increases with the working time.The fitting curve of its variation law is shown in Figure 4 and follows the law shown in Formula 3.
Where Y is the thickness of the scale and X is the working time at high temperature.
