(A) study on the impact fretting wear of steam generator tubes

Abstract

In steam generator of nuclear power system flow-induced vibration results in impact fretting-wear damage due to impacting and rubbing of the tubes against their support plates. In this paper, to examine the difference of mechanism between fretting wear and impact fretting wear, the fretting wear and impact fretting wear test were performed in the room temperature water using the same test apparatus with steam generator tube materials (Alloy 600 and Alloy 690) and tube support plate materials (405SS and 409SSS) and each wear coefficient of Alloy 600 and Alloy 690 was evaluated with work rate model applied. The experimental results show that the wear coefficients of fretting wear smaller than of impact fretting wear in the same conditions. The SEM observation of worn surfaces confirms that wear mechanisms to affect the fretting wear are adhesion and delamination, and abrasion and delamination mainly damage surfaces in impact fretting wear test. The SEM observation of subsurfaces shows that impact fretting wear tested subsurfaces have voids and cracks, while there are almost no voids and cracks in the subsurface after fretting wear test. Therefore the characteristic of impact fretting wear test is the formation of plastic deformation zone, voids and cracks. This study will describe the impact fretting wear tester, and present the results of fretting and impact fretting wear tests and the difference of wear mechanism between fretting and impact fretting wear of steam generator tube materials.