Boron nitride (BN) is identified as a strategic material for many purposes related to the integration of graphene and 2D materials in devices and the fabrication of van der Waals heterostructures. Thus, it becomes mandatory to have scalable synthesis and characterization procedures for providing suitable and reliable boron nitride material according to these three identified needs. In this work, we are interested in the TEM characterization of boron nitride films grown on copper or nickel foil by CVD, using H2 as a carrier gas and borazine as BN source. The growth on polycrystalline copper foil leads to few nanometer thick films, with a not highly crystallized turbostratic structure. These films exhibit a rough surface at the atomic scale, which is not suitable as a graphene substrate but can be used as capping material of a 2D crystal in a device. Conversely, highly crystalline boron nitride is synthesized on polycrystalline nickel foil. We performed a detailed analysis of the influence of nickel grain orientation on the structure of the BN layers in terms of morphology, thickness, orientation, domain size etc.