The Influence of Composition and Microstructure on the Abradability of Aluminum-Based Abradable Coatings

Five kinds of commercial aluminum-based abradable coatings including AlSi, Al-hBN, AlSi-polyester, AlSihBN and Al-AlSi-hBN were fabricated to perform parallel abradability tests rubbed against Ti6Al4V dummy blades at high temperature up to 450 °C and high velocity up to 300 m/s conditions. AlSi coating, which contains no additional secondary filler, only showed acceptable abradability at medium incursion rate under 450 °C, and severe blade wear or coating transfer to blade tip occurred at low and high incursion rates. Other four coatings which contain secondary fillers performed far beyond AlSi coating. It was found that not only the amount added but also the diameter of secondary fillers plays an important role in coating abradability. For the similar filler addition level, Al-hBN and Al-AlSi-hBN coatings which contain fine filler performed much better than AlSi-hBN coating with coarse filler. Shorter filler spacing in the fine filler samples is concluded to be the reason for better abradability.