Effect of adding Ta on the tribological behavior of Zr alloy after β-quenching and annealing

Abstract

In the current research, the wear properties of the Zr alloys at temperatures of 25, 300, and 600 °C under loads of 50, 100, and 150 N were investigated. For this purpose, vacuum arc melting was used to prepare Zr-2.5Nb, Zr-2.5Nb-0.5Ta, and Zr-2.5Nb-1.5Ta alloys and repeated five times re-melting. The samples were treated with a solution at 1020 °C for 30 min, annealed at 600 °C for 24 h, and then quenched in water. The microstructure analysis showed that alloys have lath and lens martensite phases with random orientations. Results demonstrated that Zr-2.5Nb-1.5Ta had the lowest wear rate among the three alloys. It was seen that at 600 °C and 150 N, the friction coefficient of the sample containing 0.5 % and 1.5 % Ta decreased by 20 % and 41 % compared to that of sample Zr-2.5Nb, respectively. Additionally, the wear rate of the sample containing 1.5 % Ta decreased by 20 % compared to that of sample Zr-2.5Nb due to the formation of a stable oxide layer containing Nb4Ta2O15 and Nb2Zr6O17, making this alloy suitable for petrochemical and shipbuilding applications. Investigation of the worn surfaces by SEM shows that by increasing the temperature, the dominant wear mechanism was transformed from abrasion/delamination to oxidation.