Study on bi-directional composite fretting wear characteristics of Zr-4 alloy tube with different phase differences under temperature conditions

The Zr-4 alloy tubes in nuclear fuel rods in pressurized water reactor (PWR) fuel assemblies were subjected to bidirectional composite fretting wear tests with different phase differences (0 degrees, 90 degrees, 180 degrees, and 270 degrees) at room temperatures and 300 degrees C by using a multi-modal fretting wear tester developed independently by the group. The experimental results show that the change in temperature as well as the change in phase difference has a significant effect on the fretting wear characteristics of Zr-4 alloy cladding tubes.The following conclusions were drawn: Among the bi-directional composite fretting tests with different phase differences, the most severe wear was observed for the bi-directional composite fretting test with a phase difference of phi = 90 degrees. Bidirectional composite fretting wear tests at 300 degrees C show more intense wear and more severe damage compared to room temperature tests. At room temperature, the morphology of the abrasion mark region is characterized by zoning, and the wear mechanism is mainly dominated by adhesion wear, abrasive wear and delamination.