Deposition behaviors and microstructural features of vacuum kinetic sprayed AlN

Vacuum kinetic spraying (VKS) has emerged as a new and innovative coating technique, in which thin and dense ceramic layers can be fabricated at room temperature via high-velocity impacts and subsequent dynamic fractures (to a few (1-10) nanometers size) of submicron-sized ceramic particles. Although several researches have been conducted to understand the bonding mechanisms of VKS coatings, the related mechanisms remain still unknown. In this regard, here, we address the influences of fracture toughness and hardness of materials on the fragmentation and bonding of various impact combinations (particle/substrate) in VKS. Four reference particle materials (having high potentials for industrial applications), such as AlN, TiO₂, Al₂O₃ and TiN with different fracture toughness (K_C) were adopted for dynamic impact modeling and simulations on various substrates (i.e. Al, Cu, steels, Ti, glass and Si that are arranged sequentially with increase in hardness) using an AUTODYN-2D 12.1. Prior to the simulations, the K_C for each particle material was estimated by nanoindentation experiments, and the value was used to tune the model more accurately. The reliability of the well-developed model was verified by comparing the simulations with the experimentally-determined deposition characteristics of some material combinations.