Autoclave grid-to-rod fretting corrosion behaviors of the Zr alloy fuel cladding with and without Cr coating through advanced characterization

The fretting corrosion behaviors and the associated mechanisms of Zr alloy claddings with and without Cr coating in the primary water (310 °C/15.5 MPa) of the simulated pressurized water reactor were studied and compared. The results demonstrated that the fretting corrosion resistance of Zr alloy cladding was improved significantly by the introduction of Cr coating. The increased fretting corrosion resistance of the Cr-coated Zr alloy cladding was mainly attributed for two reasons. Firstly, the metallic Cr had much greater hardness than the Zr alloy and the formation of the ultra-fine grains layer under the worn scar further increased its hardness. Secondly, the metallic Cr had much better plasticity than the ZrO 2 layer, resulting in better resistance to fatigue failure. • The fretting corrosion behaviors of Zr alloy claddings with and without Cr coating in PWR water were studied. • The fretting corrosion resistance of Zr alloy cladding was improved by the introduction of Cr coating. • The cross-sectional microstructure under the worn scar could be divided into a NC layer, an UFG layer, and a GD layer. • The formation of the UFG layer further increase the fretting corrosion resistance of the Cr-coated Zr alloy cladding.