Wear and fretting wear behaviour of ion-implanted Zircaloy-4

Zircaloy-4 was implanted with nitrogen at 120 keV to various total ion doses between 1 x 10(17) and 1 x 10(18) ions cm(-2) at various temperatures in the range 310-660 degrees C. The implanted surfaces were analysed by Auger electron spectroscopy (AES) and X-ray diffraction (XRD). Wear and fretting wear tests were performed at various loads under unlubricated conditions and water immersion respectively. Nitrogen implantation produced zirconium nitride and oxide which enhanced the surface hardness up to 1800 HK (0.1 N) for a total ion dose of 1 x 10(18) ions cm(-2) at 660 degrees C (300 HK (0.1 N) for unimplanted specimen). The ball-on-disc wear resistance was improved for nitrogen-implanted specimens above 500 degrees C. In addition, oxide layer and ZrN formation by nitrogen implantation in an oxygen atmosphere greatly enhanced the wear resistance of Zircaloy-4. The fretting wear resistance was enhanced by nitrogen implantation. Successful improvement of the fretting wear resistance was obtained for the specimen implanted at 550 degrees C to a total dose of 8 x 10(17) ions cm(-2).