The residual stresses build up in cold spray deposition represent a key parameter to develop compact and welladherent coatings. The physical and mechanical effects influencing the coating stress are numerous and various. They range from the peening effect due to the high velocity impact to the cooling effect due to the different thermal properties between coating and substrate materials. As a consequence, the resulting coating stress could modify several coating properties such as adhesion, structure, toughness, hardness and then reflecting on the macroscopic chemical and mechanical behavior of the coating. Different techniques are devoted to investigate stresses in different scales; for example curvature method is typically used to estimate the macroscopic mean stress, while X-ray diffraction gives more information about micro-stress and stress distribution. In the present work pure Al and AlZAl2O 3 composite coatings have been deposited by cold spray using CGT-Kinetics 3000 system upgraded in order to reach working pressure of 4 MPa and provided with the special polymeric nozzle designed for aluminum powder spraying. The particle velocities (in the range 623-765 m/s) have been evaluated using an in-flight particle optical sensor DPV2000. Residual stresses have been evaluated using three different techniques: Almen gage curvature method in order to determinate stress on calibrated Almen strips; X-Ray Diffraction and Modified Layer Removal Method in order to determine the depth profile of the stress from the surface to the interface with the substrate. Very good reliability has been verified on the results obtained with all three methods in the case of pure aluminum coatings. Peening compressive stresses, in all cases, were estimated lower than 100 MPa and their value is nearly constant along the coating thickness. Moreover, the effect of particle velocity, coating thickness and the introduction of aluminum oxide on sprayed mixture have been evaluated and discussed.Peer reviewed: YesNRC publication: Ye
