Effect of thermal-physical properties on the abradability of seal coating under high-speed rubbing condition

The tribological behaviours of two seal coatings (NiAl-hBN and Al-hBN) against Ti-6Al-4V blade were investigated under high-speed rubbing conditions by a self-developed tribology tester. The wear behaviour and the mechanism of the blades and seal coatings were studied. The maximum possible temperature (MPT) and the temperature rising rate (TRR) at the rubbing surface, which were both directly related to the mechanical strength of coating and blade, were identified as two key factors influencing the blade wear performance and the coating abradability. The MPT of Al-hBN coating was limited to a rather low level and the coating temperature resistance was poor. Hence, the coating was initially softened and blade wear was reduced or even replaced by adhesion of Al-hBN coating. The MPT of NiAl-hBN coatings could be relatively high and the TRR of NiAl-hBN was much smaller than the blade. Hence, the blade lost its mechanical superiority over the coating and was severely damaged. A dimensionless number NT was proposed based on the thermal-physical parameters of blade and coating to represent MPT and TRR and predict the degree of blade wear. The theory agreed well with the wear performance of blades coupled with NiAl-hBN and Al-hBN, as well as with other seal coatings, such as Ni-Cg and AlSi-polyester.