Thermo-mechanical discrete element modeling of the cracking in brittle film during thermal deposition process

The presence of cracks in brittle film plays a crucial role in determining the functionality and reliability of film-substrate system. It is challenging to predict and control the cracking in brittle film during layer-by-layer deposition process. Here, we develop a thermo-mechanical discrete element method that incorporates a thermal-conductive beam model to capture the cracking in brittle film during deposition process. Taking thermal barrier coating system as an example, we reveal that the temperature difference between the film and the substrate during deposition process is a key factor regulating the cracking in the film. As the temperature difference increases, there is a transition from no cracking to channel surface cracking, eventually leading to mixed cracking with coexisting channel surface cracks, interfacial cracks, and intralayer horizontal cracks, which are experimentally validated. Additionally, we elucidate how the in-plane and out-of-plane strengths of the film affect the competition of various cracks during deposition process. Then, we can create a selection map for crack regulation.