Fatigue strength of Al alloy cold sprayed with nanocrystalline powders

Nanocrystalline cryomilled and microcrystalline Al7075 powders have been deposited on Al5052 substrates using the low-pressure cold spray coating technique in order to study the effect of the powder micro/nano structure on fatigue behavior of coated samples. Microstructural characteristics and fatigue behavior of the coated structure have been surveyed through experimental tests. The powders’ size and shape distribution have been studied using scanning electron microscopy. In order to obtain the S–N diagrams, grit blasted and coated samples with different treatment parameters have been tested for fatigue at load control condition. Grain size measurement has been performed by X-ray diffraction. X-ray diffraction has also been used to measure the residual stress distribution in both the deposited material and the substrate. Surface roughness measurements have been performed on all series. It has been observed that, although the coating porosity was not zero, the fatigue limit is slightly increased by using the cryomilled powders.