Sand erosion mechanism of Ti/TiAlN multilayer coatings deposited on aluminum matrix composite at low temperature

To improve solid particle erosion resistance of 5 %TiB₂/AlSi10Mg composite, hard and adhesive Ti/TiAlN multilayer coatings with different number of layers were deposited on its surface at low temperature by multi-arc ion plating. When impacted by high-speed alumina particles at 90° and 30°, erosion resistance of the composite was significantly improved by the application of multilayer coatings. The Ti/TiAlN multilayer coating with 8 layers performed the best in all erosion condition. At 30°, detachment of surface macroparticles and intersection of cracks produced by Al₂O₃ particle flow accounted for material removal of the multilayer coatings. At 90°, intersection of the cracks including ring cracks, lateral cracks, median cracks and radial cracks developed in the multilayer coatings during impact loading and unloading accounted for erosion removal of the material. The more the number of layers in the multilayer coatings, the greater the contribution of the ring and radial cracks to the material removal. Finite element modeling showed large tensile stresses developed at both the surfaces and the undersurfaces of TiAlN layers in the multilayer coatings and also along the direction of coating thickness during impact loading and unloading, which were probably responsible for the generation of ring cracks on the surface of the top TiAlN layer, radial cracks at the undersurfaces of the TiAlN layers, and the lateral cracks inside the TiAlN layer and along the TiAlN/Ti interface. The best erosion resistance of the multilayer coating with 8 layers at 90° may be due to its architecture is beneficial for reduction of the material removal.