Steam generator fretting-wear damage: A summary of recent findings

Flow-induced vibration of steam generator (SG) tubes may sometimes result i n fretting- ear damage at the tube-to-support locations. Fretting-wear dama ge predictions are largely based on experimental data obtained at represent ative lest conditions. Fretting-wear of SG materials has been studied at th e Chalk River Laboratories for two decades. Tests are conducted in fretting -wear lest machines that simulate SG environmental conditions and tube-to-s upport dynamic interactions. A new high-temperature force and displacement measuring system was developed to monitor tube-to-support interaction (i.e. , work-rate) at operating conditions. This improvement in experimental fret ting-wear technology was used to perform a comprehensive study of the effec t of various environment and design parameters on SG tube rr ear damage. Th is paper summarizes the results of tests performed or er the past 4 yr to s tudy the effect of temperature,,water chemistry, support geometry, and tube ,material an fretting-wear. The results show a significant effect of temper ature on tube wear damage. Therefore, fretting-wear tests must be performed at operating temperatures in order to be relevant. Na significant effect o f the type of water treatment on tube wear damage was observed For predomin antly impacting motion, the wear of SG tubes in contact with 410 stainless steel is similar regardless of,whether Alloy 690 or Alloy 800 is used as tu bing material or whether lattice bars or broached hole supports are used. B ased on results presented in this paper, an average wear coefficient value is recommended that is used for the prediction of SG tube wear depth versus time.