Impact of flow-induced excitation type on fretting wear behavior of steam generator tubes

High-temperature impact fretting wear tests have been conducted worldwide since the 1970s, providing insights into the wear characteristics of nuclear power plant components. These tests typically reproduce component interface geometries, materials, and process conditions such as fluid medium, temperature, pressure, and chemistry. Most approaches assume that work rate is the primary parameter governing fretting wear dynamics, consistent with Archard’s equation. However, it is unclear whether a wear coefficient derived under one excitation type (e.g., periodic) can reliably predict component life under another (e.g., random). To address this, an experimental study was conducted using the high-temperature fretting wear rig at Chalk River Laboratories to examine the effect of excitation type on wear behavior. The study focused on a nickel alloy steam generator tube in contact with a stainless-steel support featuring a broached hole geometry. Tests were performed for 500 h in water at 280 °C under two excitation conditions. The first employed periodic excitation to simulate tube vibration from vortex-induced vibration and fluidelastic instability, while the second applied random excitation generated from empirically derived force spectra to represent turbulence-induced vibration. Tube motion and contact forces were monitored to control work rate and investigate impact statistics. Wear was assessed using profilometry and mass change to derive wear coefficients, and SEM imaging was used to assess the wear mechanisms. Results showed that, at the same work rate, random excitation caused significantly greater wear and broader impact distributions across impact angles, forces, and sliding parameters. These findings indicate that fretting wear behavior depends on excitation type as well as work rate.