Designed Ti/TiN sub-layers suppressing the crack and erosion of TiAlN coatings

Abstract

Solid particle erosion damage seriously affects the service life and operational safety of engine blades, while the erosion resistant coating is one of the effective measures to effectively improve the erosion resistance of the blade material and extend its service life. Here, we deposited the Ti/TiN/TiAlN multilayer coatings with different thickness ratio of the Ti to TiN layer on Ti-6Al-4V substrates by a home-made hybrid multisource cathodic arc system. The relationship between coating structure and coating properties including adhesion strength, residual stress, load-bearing capacity, crack resistance and erosion resistance was focused. Results showed that the Ti layer was beneficial in improving adhesion strength and reducing residual stress of the multilayer coatings, which was benefited from coordinating the deformation and absorbing strain energy induced by plastic deformation. The TiN layer was important in maintaining load-bearing capacity. Radial cracks initiation and propagation from the Ti/TiN interface occurred at most cases, while wide lateral cracks were formed only in the TiAlN layer for its high brittleness and internal stress during scratching. When the thickness ratio of the Ti to TiN layer was 1:2, the coating exhibited the best combination of hardness, adhesion strength, crack resistance, and load-bearing capacity. As a consequence, the coating behaved the lowest erosion rate of 0.060 ± 0.0002 mg/g and 0.024 ± 0.0068 mg/g at the erosion angle of 90° and 30°, respectively.