Effects of blade material characteristics on the high-speed rubbing behavior between Al-hBN abradable seal coatings and blades

Abradable seal coatings have been widely used in aero engines to reduce gas path clearance. Research has been performed to evaluate the abradability of the seal coating. In addition, the high-speed rubbing test rig has been employed to simulate the interaction between the seal coating and blade. However, almost all previous studies tested blades made of one type of material. In real engines, the blade material for a seal coating is changeable. In this work, blades made of different titanium alloys were tested and rubbed against the same Al-hBN seal coating. Macro-morphology and micro-morphology observations with scanning electron microscopy (SEM) were employed to examine the wear behavior of the blade-coating couple. The results indicated that the Ti6Al4V blade exhibited the most severe coating adhesions and almost no blade wear; the Ti-8Al-1Mo-1V blade experienced less coating adhesions; and the Ti-5Al-2Sn-2Zr-4Cr-4Mo blade exhibited the least coating adhesions. The mechanical strengths at room and high temperatures and the rub performances during the single pendulum scratch test were checked to find the relationship between the mechanical properties and high-speed rub performances. Unfortunately, high mechanical strength did not appear to guarantee the absence of blade wear, and the thermal properties of the different materials blades were identified as the main reason for the different wear behaviors.