Effect of alloying element Mo on thermal fatigue properties of high strength gray cast iron

The effect of alloy element Mo on the thermal fatigue properties of gray cast iron was analyzed by comparing two groups of samples B, D, C and E. Fig. 1 shows the thermal fatigue crack growth morphology of test gray cast iron samples B, D, C and E after 500 thermal cycles. It can be seen from the comparison of B and D in Figure 1 that some secondary cracks will sprout on the main thermal fatigue cracks of sample B, and the secondary cracks will continue to expand, and there are few secondary cracks formed in sample D; Compared with the C and e diagrams in Figure 1, it is also found that there are more secondary cracks on the main crack of sample C, the main crack is wider, and there are fewer secondary cracks on sample E.

The thermal fatigue crack length of B, D, C and e samples of experimental gray cast iron after 500 thermal cycles. It can be seen that the main crack length of B and C samples without alloy element Mo is longer and there are more secondary cracks. Therefore, we can draw a conclusion that the addition of alloy element Mo helps to improve the thermal fatigue performance of gray cast iron, mainly because Mo can form a dense alloy oxide film, improve the phase transformation temperature, and strengthen the matrix, so that the matrix has better high-temperature strength, It can withstand large thermal stress.

Fig. 2 shows the crack propagation diagram of the experimental gray cast iron on the matrix after 500 thermal cycles. It can be seen that the crack of sample B without alloy element Mo is wider, the secondary crack of sample C is more, the crack of sample d with alloy element Mo is narrower, and the secondary crack of sample e is less.