Ceramic conversion treatment of zirconium alloys to combat corrosion wear

Abstract

A series of ceramic conversion treatments have been conducted on Zr702 and Zr705 zirconium alloys by thermal oxidation at temperatures ranging from 400 to 700°C for 3–30 h. A wide range of material characterisation techniques were used to investigate the microstructure, composition, phase constituent, load bearing capacity and wear properties of the surface treated zirconium alloys. Experimental results show that after ceramic conversion treatments, the surfaces of Zr702 and Zr705 alloys can be converted to a ceramic layer consisting of α-ZrO₂ and β-ZrO₂; the optimal ceramic conversion treatment conditions for Zr702 and Zr705 alloys are 600°C/10 h and 600°C/3 h respectively; Zr705 alloy has a better response to ceramic conversion treatment than Zr702; and the wear resistance of the optimally treated zirconium alloys can be improved by more than 200 times. The wear mechanisms of both untreated and ceramic conversion treated zirconium alloys are discussed. The dominant wear mechanisms changed from severe adhesive wear for the untreated zirconium alloys to mild abrasive wear for the ceramic conversion treated materials.