Environment effects on the reciprocating wear of Inconel 690 steam generator tubes

Reciprocating sliding wear experiments have been performed in various environmental conditions, such as various temperatures, air and water environments to examine the wear properties of Inconel 690 steam generator (S/G) tubes. For present study, the test rig was designed to examine the reciprocating and rolling wear properties in high temperature. The test rig consists of pressure vessel, electric heater, reciprocating, rolling and loading units. Tests were performed at constant applied load and sliding distance to investigate the effects of temperature and environment. Then, the worn surfaces were observed using scanning electron microscope to investigate the wear mechanism. In water environment, the wear loss increased with temperature between 25 and 150 °C. Beyond 150 °C, the loss decreased with increasing temperature. However, in air environment, the loss decreased with increasing temperature in all temperature ranges. The wear loss variation with temperature was due to the formation of oxide layer. It was assumed that the layer was formed by wear debris sintering, cold welding or oxidation mechanisms and these properties were varied with tests temperatures and environments, which was confirmed by identification of the oxide layer by worn surface observation.