Residual Stresses in Cold Spray Additively Manufactured Hollow Titanium Cylinders

In cold spray additive manufacturing (CSAM), the severe plastic deformation of the input powder particles leads to an accumulation of residual stresses, the magnitude of which is affected by process conditions. In the current study, the effects of traverse speed and powder feed rate on the residual stress state were investigated in commercially pure titanium cylinders produced by CSAM. Residual stress measurements were made in a grid pattern covering the 2D cross section using the KOWARI neutron diffractometer at ANSTO, Australia, and selected results were validated using the contour method. It was found that the thermal effect was dominant on the residual stress state generating a tensile state near the inner and outer surfaces of the cylinder walls while compressive residual stresses tend to accumulate in the center of the wall. The residual stresses were dominated by thermal stresses at low traverse speed, while peening becomes more critical at high traverse speeds. Increasing the powder feed rate increased the magnitude of the residual stresses. High traverse speeds and low feed rates are beneficial for producing 3D parts by CSAM. However, slow traverse speeds are more detrimental than high feed rates for a given layer thickness.