Facet identification in textured polycrystalline coatings by EBSD-aided SEM trace analysis

Competitive growth usually occurs during deposition of polycrystalline coatings and is associated by the formation of crystal facets. Knowing the facet planes in the crystal coordinates is thus essential for understanding the coating growth process and optimizing corresponding experimental parameters. However, the crystal facets of polycrystalline coatings have not been explored enough due to a lack of easy-to-use experimental methods. In this work, we apply an electron backscattered diffraction (EBSD)-aided scanning electron microscopy (SEM) trace analysis for determining the crystal facets of the chemical vapour deposition (CVD) polycrystalline (Ti,Al)N and Ti(C,N) coatings. Using this method, the crystal orientation of an interesting grain relative to the specimen coordinates is first determined by the EBSD point analysis, and the crystal orientations of edges shared by neighbouring facets are then determined using trace analysis. Finally, the facet normals are calculated by the cross-product of the crystal orientations of edges on the corresponding facet. The (Ti,Al)N coating is found to have {100} crystal facets, which is consistent with the results obtained using transmission electron microscopy in previous work. The Ti(C,N) coating is found to have {211} crystal facets. In principle, the method proposed in this work can be applied to any crystals with planar facets and sharp edges. A possible improvement of the method is also discussed.