Deposition mechanism and fracture characterization of 434 stainless steel HOVF coating on T6061 aluminum alloy

434 stainless steel coatings have been applied T6061 alloy using High-Velocity Oxygen Fuel (HVOF) as a deposition technique for surface performance improvement. The relationship between the coating's deposition characteristics of thickness, homogeneity, porosity, and hardness and the spraying parameters of mainly the number of sprayed-layers and spraying distance was revealed. The coating's fracture behaviors was further studied using three-point bending and digital image correlation (DIC) technology, which allows the observation of the crack progression and record the stress distribution on the coatings. Results showed that the crack progression always occur at the oxides between the different sprayed layers or surrounding semi-melted feedstock particles, the crack progression mode is mainly depending on the number and location of oxides in the coating. Then, the crack progression mainly continued through the interface between sprayed layers while the oxide content approach or exceed a critical value of 12 %. Finally, a model for the coating fracture mechanism was established to explain the interface bonding performance between the coating and the substrate.