The transformation of fretting corrosion mechanism of zirconium alloy tube mating with 304 stainless steel in high temperature high pressure water

Abstract

Studying the fretting wear mechanism of zirconium alloy in high temperature high pressure water is of great importance for understanding the failure behavior of fuel assembly. In this work, the tangential fretting wear of zirconium alloy tube at different displacement amplitudes (40 µm and 80 µm) and normal forces (6 N and 12 N) was investigated in high temperature high pressure water. The results show that the wear depth and wear volume of zirconium alloy tested at 6 N-80 µm are the highest among all the tests. When the testing condition is 6 N-80 µm, the fretting is located in the gross slip regime. Oxidation and abrasive wear dominate the fretting wear behavior. The increase in normal force and decrease in displacement reduces the relative sliding distance between the contact interfaces, which reduces the ejection of wear debris and changes the wear mechanism. When the test conditions are 6 N-40 µm and 12 N-40 µm, the fretting regime is located in the partial slip regime, and the dominant wear mechanisms are adhesive wear and oxidation. Under the synergistic effect of mechanical wear and high-temperature water corrosion, a dual-layer structure oxide scale is formed on the worn area. The mixed oxide layer with loose and porous structure is formed by the accumulation of granular wear debris, while the dense inner oxide layer is mainly formed by oxidation of the matrix alloy. Fretting wear accelerates material corrosion by wear debris refinement and cracking. The integrity of the oxide layer is negatively correlated with its thickness. As the thickness of the oxide layer increases, more cracks can be observed in the oxide layer.