Effect of Normal Force on Fretting Wear Behavior of Zirconium Alloy Tube in Simulated Primary Water of PWR

The effect of normal force on fretting wear behavior of zirconium alloy tube mated with grid dimple in simulated primary water of pressurized water reactor nuclear power plant was investigated. Results showed that the maximum wear depth, wear volume and wear coefficient of Zr alloy tube in simulated primary water at 315 degrees C gradually increased with increasing normal force, while the friction coefficient gradually decreased. Fretting process could be divided into four stages according to the variation of friction coefficient during test. When normal force exceeds 30 N, the fretting regime would transition from gross slip regime to partial slip regime after 3 x 10(7) cycles. Delamination was aggravated with increasing normal force, while abrasive wear became slighter. A thicker third-body layer with monoclinic ZrO2 was formed by the tribo-sintering mechanism under higher normal force. In addition, the schematic evolution processes of delamination and third-body layer formation were displayed according to morphology observation.