Modeling and Finite Element Method Analysis of Fatigue Failure of 8.72Cr-0.9Mo Steel Boiler Heat Tube

Abstract

In power plant heat tube is the main component where the water is changed to high-pressure steam, it operates under corrosive and high temperature environment. Corrosive environment and cyclic temperature fluctuation cause fatigue on boiler heater tube, and which degrade life of the component. This paper presents corrosion rate by volumetric pit growth, crack initiation and crack propagation of boiler heat tube for power plant under cyclic thermal load. 8.72Cr-0.9Mo steel is one of the steel type which mostly used nowadays as boiler heat tube. Volumetric pit growth rate approach used for crack initiation and energy release rate approach (J-integral) used to find crack propagation phenomenon. Temperature is taken in the interval of 25 , and it has a significant effect on rate of chemical reaction (corrosion rate) and material properties. The results show 906Mpa and 895Mpa thermal stress induced at crack tip at from analytical and FEM respectively. And also energy release rate results are from analytical and FEM respectively. From the result, material reach fatigue limit in the range of low cycle fatigue having the value less than cycles. The existence of corrosion reduces crack initiation cycles since crack initiation is speed up by the presence of corrosion.