Impact of yttrium on structure and mechanical properties of Cr–Al–N thin films

Cr 1 − x Al x N coatings are known for superior mechanical and thermal properties, which make them promising candidates for advanced machining and high temperature applications. Their oxidation resistance can further be improved by alloying oxygen active elements such as yttrium, which promote growths of dense and adherent oxide scales. Based on x-ray diffraction and transmission electron microscopy studies the authors can conclude that our films with an Al∕Cr ratio of ∼1.2 exhibit a single phase NaCl-type crystal structure for the investigated Y-content variation. With increasing YN mole fraction from 0% to 8% the lattice parameter increases from ∼4.11to4.18Å, the hardness increases from ∼31to38GPa, the indentation modulus decreases from ∼497to488GPa, and the residual biaxial compressive stresses decrease from ∼−1.6to−0.6GPa, respectively. The mean crystallite feature size is found to be in the range of 28–43nm for the coatings investigated.