Mechanical, fretting wear and tribocorrosion properties of CrxN coatings on Zr-4 alloy prepared by double glow plasma alloying technology

Abstract

Cr-based coatings show great potential for serving as accident tolerant fuel (ATF) claddings in pressurized water reactors (PWRs). In this paper, Cr_xN coatings were produced on Zr-4 alloy by double glow plasma alloying technology at different Ar/N₂ ratios (7:3, 5:5, and 3:7). The Cr_xN coatings consist of CrN and Cr₂N phases and without the formation of (Zr, Cr) phase. The hardness (H) and elastic modulus (E) increase with the rise of nitrogen flow rate, which is consistent with the nitride content on the surface. Under the 3:7 Ar/N₂ ratio, the highest H/E and H³/E² values indicate the Cr_xN coating has great toughness and load bearing capacity, the critical load of the coating in scratch test is 26.2 N. The coating has a low volumetric wear rate, which indicates excellent resistance to fretting wear, the main wear mechanisms of coated Zr-4 alloy were observed to be abrasive wear, adhesive wear and oxidation wear. The tribocorrosion test results show that the coating (Ar/N₂ ratio = 3:7) has the best resistance to the synergistic effects of wear and corrosion. In addition, a deep understanding of this paper can provide a new method for the service of ATF coatings on Zr alloy cladding.