Preparation of oxide coating on Ti30Zr5Al3V alloy via plasma electrolytic oxidation and its tribological behavior

Abstract

In this study, plasma electrolytic oxidation (PEO) method is used to improve wear resistance of a novel TiZr-based alloy (Ti30Zr5Al3V). Different applied voltages (300, 400 and 500 V) and processing time (60, 180, 420, 600, 1200, and 1800 s) are used to prepare the oxidate coating. The compositions of the PEO coating are similar, including anatase, rutile, srilankite, and Al2O3 phases, under different voltage and processing time conditions. Besides, amorphous phase can be detected with increasing the voltage or processing time. The surface morphology of the coating is analyzed, and the average size of the micro-pores increases from ∼3.52 μm to ∼3.68 μm and then decreases to ∼3.07 μm with increasing the voltage from 300 V to 500 V. However, the size presents different variation trends after being treated with different processing time. The average size increases from ∼1.47 μm to ∼4.41 μm when the processing time increased from 60 s to 180 s. With further increasing the processing time, the size decreases to ∼1.65 μm because the “B” type discharge becomes dominant. At the processing time of 1800 s, the micro-pores size increases to ∼4.05 μm. The cross-section of PEO-treated samples show that obvious separation can be observed when increasing the applied voltages or processing time. The thickness of oxidate coating increases monotonously under the applied voltage condition, while the thickness increases firstly and then decreases to ∼9.6 μm under different processing time. Moreover, the tribological behavior of PEO-treated Ti30Zr5Al3V alloy is investigated. The results show that the oxidate coating exhibits a higher COF value but lower wear rate. When compared with the other applied voltage conditions, the 500 V PEO-treated show the best wear resistance. For the processing time, the samples after being treated with 1200 s possess better wear resistance.