Temperature and stress management in cold sprayed deposits

Material deposition in cold spraying occurs in solid state and thus avoids undesired effects of melting and solidification. However, residual stress conditions in cold sprayed coatings could limit possible part performance. The temperature distribution and thermal history of the cold sprayed components has significant influence on stress distribution and thus deposition and part quality. The present study investigates the effect of substrate material and nozzle traverse speed (as a secondary parameter) on effective temperatures and residual stress distributions of titanium-grade 1 deposits. The results demonstrate that substrate material properties and nozzle traverse speeds have significant influence on residual stresses of the cold spray deposit. It is understood that coefficient of thermal expansion (CTE) difference of the coating and substrate materials has significant effect on residual stress state. On the other hand, the residual stresses change from more compressive to more tensile state as the temperature of the components increases by decreasing the nozzle traverse speed. These findings indicate that thermal parameters affect residual stresses substantially. Thus, by adjusting the kinematic parameters and reducing maximum reached local temperatures within the part, more favorable stress states of the finished component can be obtained. The attained knowledge is essential for the development of high-quality deposits and the selection of the best strategies for repair and additive manufacturing applications.