*3.4.2 Mechanical properties for TiCN, BCN and CrAlN coatings nitride coatings*

After the structural and morphological studies presented above, the mechanical properties of TiCN, CrAlN and BCN coatings deposited on AISI 1045 steel substrates presented in the **Figure 11a** were analyzed by means of load-displacement curves. **Figure 11b** and **c** show the hardness and elastic modulus of the coatings, where values were obtained for TiCN (H = 28 Gpa, E=224 Mpa), followed by CrAlN (H=30 Gpa, E=251 Gpa= and then BCN (H=33 Gpa, E=335 Gpa). These results obtained are attributed to surface factors such as those presented by AFM (**Figure 7**), where a direct relationship between the roughness and grain size is show. Thus, having a smaller grain size results in a higher grain edge density and these grain edges act as impediments to the movement of dislocations. Thus, higher shear stresses are required for the dislocations to pass through these obstacles, so these coatings will have better mechanical properties [27–30]. On the other hand, the elastic modulus (E) of coatings is related to the type of material, but not to its microstructure; in this sense the elastic modulus (E) depends on its crystalline structure and microstructural factors such as the lattice parameter.
