Effect of the cycle number on fretting wear behavior of alloy 690TT tube in high-temperature pressurized water

Abstract

In high temperature water, the fretting wear behavior of Alloy 690TT against Type 405 stainless steel were investigated under different cycle numbers. Results indicated that the change of wear coefficient strongly depended on wear stage and oxide type of compact third body layer (TBL). Within 100000 cycles, the wear gradually entered the stable wear stage from the running-in stage, and the wear coefficient changed conformed to power law distribution. When the number of cycles exceeded 100000, a smooth and compact TBL composing of Fe2O3 and spinel oxide was formed on the surface of the wear scar, the wear coefficient changed slowly. With the increase of cycle number, the percentage of NiCr2O4 and NiFe2O4 in the surface oxide gradually decreased, while that of Fe2O3 gradually increased. The formation of cracks parallel to the surface was related to the surface stress field distribution. During the fretting process, the state of the stress component parallel to the surface changed from tension to compression, prevented cracks from moving to the matrix deep expansion, resulting in the crack propagation direction parallel to the wear surface in the TBL. Finally, the relationship between stable wear life and critical wear depth was established, and the stable wear life was related to running-in wear volume (V0) and stable wear rate (γa).