Study of PEO on the fatigue behavior of titanium alloy Ti-6Al-4V

In this study by applying plasma electrolytic oxidation (PEO) coating on titanium alloy Ti-6Al-4V its fatigue behavior was studied. The results were compared in the presence or absence of the coating. Scanning electron microscopy (SEM) were used to determine the chemical composition of different phases as well as analyzing the microstructure and cracks’ nucleation and propagation and the coating hardness was measured by micro hardness tester. Fatigue test results showed that the fatigue life of the uncoated specimens was longer than the coated specimens. Comparing the images of the fracture surface of the coated specimens and the uncoated specimens in the same surfaces showed that the nucleation of fatigue cracks was appeared in one area in the uncoated specimens while the nucleation of fatigue cracks in coated specimens appeared in multiple areas. According to the microscopic images the coated surface had many pores which causes the nucleation to begin with the coating. The results of the test micro surveys of coverage shows that the hardness of the coating over the layer below it and makes it crack initiation of coverage to begin.