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We first analyze the properties of frontal collisions of two growing interfaces considering different short range interactions between them [Phys. Rev. E 97, 040801(R) (2018)]. Due to their roughening, the collision events spread in time and form rough domain boundaries, which defines collision interfaces in time and space. We show that the statistical properties of such interfaces depend on the kinetics of the growing interfaces before collision, but are independent of the details of the interaction and of their fluctuations during the collision. Those properties exhibit dynamic scaling with exponents related to the growth kinetics. However, their distributions may be non-universal for e.g. two KPZ interfaces. These results are supported by simulations of lattice models with irreversible dynamics. Secondly, we model the formation of a grain boundary of a two-dimensional material by considering attachment and detachment of atoms at the two interfaces and a constant atomic flux towards the gap between them. While a low flux produces an evolution similar to that of the irreversible models during the collision, for a high flux we observe a faster roughening and, after the collision, a decay of the boundary roughness to a value smaller than that obtained with low flux in a much shorter time. The application to graphene growth is currently under investigation.