Reciprocating Wear Studies of Inconel 718 and Mod.9Cr–1Mo Ferritic Steel by Surface Profilometric Characterization

Abstract

The Indian prototype fast breeder reactor (PFBR) is a pool-type reactor in which the steam generator employs liquid sodium as coolant. Modified 9Cr–1Mo is the construction material for steam generator, owing to its excellent high-temperature mechanical properties. Nickel alloy 718 has been used for the tube bundle support structures due to its excellent high-temperature properties and its compatibility with liquid sodium. The coolant sodium is responsible for the flow-induced vibration in the steam generator tubes which in turn leads to the reciprocating fretting wear in the components. This wear is undesirable for both life perspective and functionality. It is important to study the wear of the components, such as the heat exchanger tubes of Cr–Mo steel and the support structures by simulating the industrial operating atmosphere. As a groundwork, reciprocating wear tests are planned and the test matrix has been formulated to study the wear characteristics of Inconel 718 against Al2O3 balls and 9Cr–1Mo. The tests were carried out in frequencies of 3, 6 and 9 Hz and varying temperatures such as room temperature (RT), 100 and 150 ℃. Optical microscopy is carried on the tested samples to study the metallography. Surface profilometer is employed to characterize the worn scars of the tested specimens and thereby concluding the mode of material removal during the reciprocating wear. Different surface roughness parameters on the scar were studied and compared with the parameters taken for study.