Abstract
Thermal fatigue crack initiation and propagation tests for boiler steel SB410 were conducted up to 100 cycles at 573,673,773 and 873K by use of a laboratory made thermal fatigue testing apparatus. The higher the heating temperature, the lower the number of cycles for crack initiation was. The higher the heating temperature, the faster the crack propagation rate was. The thermal fatigue crack was observed by optical microscopy. Plural cracks were observed at 873K, and the crack tip was branched. While, the crack length at 573K was very short. The higher the heating temperature, the longer the crack was.
