Improving the tribological and corrosion properties of Zr702 and Zircaloy-4 alloys by Ceramic Conversion Treatment

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Zhang, Shiling (2017). Improving the tribological and corrosion properties of Zr702 and Zircaloy-4 alloys by Ceramic Conversion Treatment. University of Birmingham. Ph.D.

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Abstract

Despite of the wide application of zirconium and its alloys, wear and corrosion of zirconium components are major issues for demanding applications. To this end, ceramic conversion (CC) treatments at different temperatures for varying time were therefore carried out on both Zr702 and Zircaloy-4 alloys. In addition, first trial of duplex surface treatment was conducted on Zr702 alloy to study the response of the CC formed ceramic layer to oxygen boost diffusion (OBD) and to increase the oxygen diffusion zone (ODZ). Results showed increased anti-corrosion and anti-wear properties due to the generation of dense ceramic layer (mainly m-ZrO\(_2\) and t-ZrO\(_2\)) supported by a hardened diffusion zone on the surface. Pitting corrosion of as received Zr702 and Zircaloy-4 can be eliminated; improvement in wear resistance at best treatment condition has increased 3.7×103 and 8.9×102 times for Zr702 (530°C/10hrs) and Zircaloy-4 (500°C/10hrs) respectively. The main wear mechanism has changed from adhesive wear for the as-received materials to mild abrasive wear of the CC treated samples. OBD treatment in both two-step and three-step duplex surface treatments can further increase the wear performance of Zr702 due to the reduced porosity and cracks in the oxide layer and thickened oxygen diffusion zone.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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