Surface microstructures and high-temperature high-pressure corrosion behavior of N18 zirconium alloy induced by high current pulsed electron beam irradiation

Abstract

The aim of present paper was to study the microstructural evolution and the high-temperature high-pressure corrosion behavior of N18 zirconium alloy prior and after high-current pulsed electron beam (HCPEB) surface irradiation. Observations of microstructures showed that after HCPEB irradiation, the surface layer of the sample was melted, inside which gradually refined grains, martensites and their internal twin substructures were obtained. Meanwhile, second-phase particles (SPPs) were dissolved into the matrix within the modified layer, and alloying elements Fe, Cr, Nb were supersaturated in Zr-based solid solution. Besides, high residual compressive stress was unceasingly accumulated in the surface layer with the increasing of pulses. After exposed at 500 °C/10.3 MPa superheated steam for 30 days, the corrosion resistance of multiple-pulsed samples, particularly the 25-pulsed one, was obviously higher than that of the initial sample. The combined action of high residual compressive stress, supersaturated alloying elements, selective purification effect and abundant structure defects in the modified layer helped improve the corrosion resistance.