Creep characterization and damage assessment of long term service exposed P-22 grade of steel

This paper deals with damage assessment of 17 years servic-exposed P-22 grade of steel used in main steam pipe of a boiler in a thermal power plant. Experimentally determined conventional creep data under identical testing condition were used in the present investigation. The value of (ratio of rupture strain to Monkman-Grant constant)infers that both service exposed as well as virgin material are ductile at at 550C/145 MPa. It was observed that ductility in the service exposed material decreases with decrease in temperature at constant stress (145MPa). It is also appa-rent that the values of strain fraction and life fraction are identical. A degree of scatter is observed in the Monkman-Grant constant (Es) value under identical test condition. Fractographic features and structure-property correlation study with optical, scanning and transmission electron microscopy were useful in predicting probable occurence of experimental scatter.