*3.4.3 Mechanical properties for Si3N4 coatings nitride coatings*

**Figure 12** shows the results of hardness (H) and reduced elastic modulus (Er) of the Si3N4 coating deposited on an AISI 316 steel. Through these results it was possible to determine that this coating presented a higher resistance to being indented in comparison to the Al2O3 coating. This behavior is attributed to surface factors such as a smaller grain size, which means an increase in the amount of grain boundaries, which act as impediments to the displacement of dislocations. On the other hand, the presence of compressive stresses generated during the deposition process contributed to the increase in the hardness of this coating. Thus, the Si3N4 coating obtained the best mechanical properties such as hardness (H) and reduction elastic modulus (Er).
