بررسي تغيير پارامترهاي زيرساختاري و ابعادي فولادهاي آستنيتي بويلر براي تعيين ميزان آسيب وارده بر لوله ها

Investigation on Micro structural and Dimensional Parameters of Austenitic Boiler Tubes for Damage Assessment

Austenitic alloys are used in critical parts of the boilers, due to their relatively good creep and corrosion resistance. Because of installation of austenitic tubes in critical parts of the boiler, access to relevant methods in order to evaluate their extent of damage is very important Considering the fact that changes in their microstructure is incomparable to other metal parts in the boiler, finding a relevant method to evaluate the extent of damage of austenitic tubes will enable the operators to plan their repair and replacement schedules. In this paper degradation and its development in Austenitic alloys is studied . The formation of sigma and carbide phases are considered, with their deleterious effect on corrosion property. As the growth and development of the grain size is a function of time and temperature, the changes of grain size with respect to these factors are presented. In this case, an average size of the majority grains in each sample is taken as representative of the sample. Beside these microstructural considerations the rate of thining of the tubes are compared. Due to the uniqeness of microstructural development, grain size and thining rate, these methods can be considered as a unique method for damage evaluation and study of austenitic boiler tubes.