State of residual stress in laser-deposited ceramic composite coatings on aluminum alloys

The nature and magnitude of the residual stresses within laser-deposited titanium carbide (TiC) coatings on 2024 and 6061 aluminum (Al) alloys were investigated. Macro- and micro-stresses within the coatings were determined using an X-ray diffraction method. Owing to increased debonding between the coating and the substrate, the macro-stresses were found to be compressive and to decrease in magnitude with increasing processing speed. The origin of the macro- and micro-stresses is discussed. To that end, transmission electron microscopy observations showed no evidence of plastic deformation within selected coatings. The micro-stresses in the TiC particulate and aluminum matrix phases within the coatings were found to be independent of the amount of debonding. This study could assist in optimizing the processing parameters to fabricate composite coatings for specific applications.