Investigation on fretting wear of NiCrAlY coatings at elevated temperature

Tribological properties of MCrlAlY (M = Ni, Co, or Ni and Co) coatings are well established under sliding conditions. However, the tribological properties of MCrAlY coatings under fretting conditions, typically encountered in blade-disk dovetail connection of aero engines, are yet to be further studied. The present study aims to investigate the elevated-temperature fretting wear behaviors and mechanisms of a NiCrAlY coating deposited on a gamma-TiAl substrate. Scanning electron microscope, energy dispersive spectrometer, and Raman spectrometer were utilized to study the wear scars and tribolayers. Transmission electron microscope and nanoindentation tests were utilized to elucidate the structural and mechanical properties of the tribolayers. The results revealed that, large areas of sea-shape tribolayers formed on the NiCrAlY coating and resulted in the low wear rate and friction coefficient. While for the gamma-TiAl substrate, small areas of island-shape tribolayers formed, and insufficient to protect the alloy from severe abrasive wear, delamination, and adhesive wear. The formation of the sea-shape tribolayers was found to be derived from the high diffusion coefficients in the oxides. In addition, the wear of the counterpart nickel alloy was not aggravated with the NiCrAlY coating, since sea-shape tribolayers also formed on the counterpart.