Paper Title
Effect of Double Austenitization Treatment on Fatigue Crack Growth Behavior of Modified 9CR-1MO Steel

Abstract
In the present investigation, fatigue crack growth behavior and tensile properties of Modified 9Cr-1Mo steel have been investigated. The modified 9Cr-1Mo steel is subjected to double austenitization treatment (a two stage normalizing at 1050 ºC/2h/water quenching+1050 ºC/2h/air cooling) followed by tempering at 750 ºC for 2h in order to refine microstructure and improve precipitation state. Microstructure parameters such as grain size, lath width. precipitate size and area fraction of precipitates were examined and correlated with tensile and fatigue crack growth behavior. The results showed that double austenitization treatment causes an improvement in area fraction of precipitates and reduction in grain size, which leads to improvement in fatigue crack growth and tensile properties of Modified 9Cr-1Mo steel. Fractograph shows a typical type of tensile fracture with radial cracks and axial splitting. The severity of such radial cracks and axial splitting are influenced by double austenitization treatment. Keywords - Modified 9Cr-1Mo Steel, Fatigue Crack Growth Rate, Double Austenitization Treatment