Effect of Mean Stress on Ratcheting Fatigue Behavior of Modified 9 Cr–1 Mo Steel at RT and 600 °C

Cyclic accumulation of plastic strain under asymmetric cyclic stressing is known as ratcheting. During the last a few decades, a large number of investigations have been carried out on ratcheting fatigue behavior of several structural materials, in experimentation as well as modeling. Modified 9 Cr–1 Mo steel is widely used in petroleum industries, chemical processing and thermal/nuclear power plants, and is also a candidate material for steam generator components in liquid metal cooled fast breeder reactors because of its mechanical properties, thermal conductivity and microstructural stability at elevated temperature. The present investigation basically deals with the effect of mean stress on ratcheting fatigue behavior of this steel at RT and 600 °C and comparison of the ratcheting fatigue behavior at these temperatures, at the normalized mean stress of 0.26 and 0.20, respectively. The results are discussed in terms of the effects of the uniform elongation, deformation behavior and microstructural stability.