Cold Spraying of Ti2AlC MAX-Phase Coatings

Cold spraying was applied to deposit Ti2AlC on different substrate materials. The study of single impacts by scanning electron microscopy indicates that bonding of the first layer is mainly attributed to the deformation and shear instabilities occurring at substrate sites. Nevertheless, as compared to the feedstock particles, the splats appear flattened by the impact. This deformation seems to be attributed not only to local, internal shear but also to internal fracture. By applying up to five passes under optimized spray parameters, Ti2AlC-coatings with thicknesses of about 110-155 mu m were achieved. XRD analysis of the coating proved that the crystallographic structure of the feedstock was retained during cold spraying. The coating microstructures show rather low porosity of about < 2%, but several cracks between spray layers. Successful build-up of more than one layer can probably be attributed to local deformation of the highly anisotropic Ti2AlC-phase.