Two series of CrN_x coatings have been deposited in an industrial PVD set-up.It is shown that for an increased ion bombardment on the growing film the hardness (H) and Young's modulus (E) are independent on composition.For these hard coatings the elastic strain to failure or polasticity limit (H/E) is 0.11.The coating fails long before it is stretched to its plasticity limit.Deformation of the coating by 1% already leads to crack formation.It is argued that the cause of this failure is the low work of fracture of the coating combined with flaws in the coating.
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