Enhancing erosion resistance of ceramic/metal multilayer coating by crack inhibition design

Erosive damage of nitride coatings is predominantly attributed to coating delamination caused by crack initiation, propagation, and coalescence. For brittle nitride coating materials, inhibiting the crack initiation and propagation within the coating may enhance their erosion resistance. This paper focuses on TiAlN/TiAl multilayer coatings, and by increasing the thickness of the metallic sublayers, the initiation and propagation of cracks in ceramic/metal multilayer coatings are significantly suppressed. As the metallic sublayer thickness increases from 1 to 4 μm, the TiAlN/TiAl coating erosion rate decreases from 0.032 to 0.002 mg⋅g⁻¹, resulting in an improvement in the erosion resistance of over ten times. Based on the failure mechanism of ceramic/metal multilayer coatings under sand erosion conditions and finite element analysis, there are two reasons for improving the erosion resistance of ceramic/metal multilayer coatings by increasing the toughness of the metal layer. On one hand, increasing the thickness of the ductile metal layer can effectively reduce the maximum tensile stress value on the coating surface and decrease the equivalent plastic deformation of the ductile metal layer, thereby improving the crack initiation suppression ability of the coating. On the other hand, increasing the TiAl layer thickness effectively suppresses the downward propagation of longitudinal cracks and the coalescence of transverse cracks in nitride coatings. This research proposes a new approach for enhancing the erosion resistance of nitride coatings.