Abstract
The increase of operating parameters (usually pressure or temperature) of high temperature facilities such as power plant or internal combustion engine requires the development of higher strength alloys. For example, in order to improve the thermal efficiency of power plant, there has been a strong drive to develop heat resistant steels with excellent creep, high temperature fatigue and thermal fatigue resistant properties. In this study, the test material was P122 alloy which has been developed for ultra super critical power plant. To measure DeltaKth values, fatigue tests were performed by DeltaKth decreasing method at three different microstructures (Base metal, HAZ, Weld metal) regions. Also DeltaK increasing tests were performed to investigate fatigue crack growth rate after DeltaKth values were found at each microstructure. Tests were performed with compact tension specimens at 600 700 Delta with the loading frequency of 20Hz. Experimental results of DeltaKth were analyzed to determine the effect of microstructures at different test temperatures.
Keywords: Fatigue, High temperature, HAZ (Heat Affected Zone), DeltaKth, P122