Prediction of the Flattening Ratio and Hardness of Cold Sprayed Deposits

Cold spray technology is a solid-state deposition process where solid particles are accelerated to very high velocities by expanding a compressed gas through a supersonic nozzle. The particles impact a substrate located approximately 25 mm from the exit plane of the nozzle. Predicting the deformation and resultant properties helps in developing process parameters and tailoring coatings to get the desired properties. In this study, aluminum, copper, and nickel coatings were produced using a range of process parameters that produced different particle impact velocities. The Hollomon power law relationship and Johnson-Cook flow stress model were utilized to predict the hardness of cold spray coatings. Results showed there was good agreement between the predicted and measured hardness of the respective coatings. Additionally, a methodology was developed to measure deformation in the form of a flattening ratio of the deposited particles. There was good agreement between the predicted and measured flattening ratio, especially for the Al and Ni feedstock powders.