Investigation of the Residual Stress and Microstructure of Wire Plus Arc Additive Manufactured Components Using F22 Steel - FS3

Wire plus Arc Additive Manufacturing is a manufacturing method under investigation for production of subsea components using F22 steel. During manufacturing, the steel undergoes repeated heating and cooling cycles resulting in a complex microstructure and residual stress field. Three samples were analysed, which Technip FMC provided, in different heat-treated conditions: as-printed and two proprietary heat-treated samples, HT1 and HT2. Optical microscopy and Scanning Electron Microscopy were utilised to investigate the microstructure and it was found for all three samples that the microstructure was largely Bainitic. X-ray Diffraction was performed to analyse the residual stresses and it was found for all three samples that the residual stresses were compressive, with the as-printed sample having higher compressive stresses than both HT1 and HT2. A Vickers hardness test was completed, showing a fluctuating hardness profile for the as-printed sample where both HT1 and HT2 had a linear profile. Following equations derived in literature for the 0.2% offset Yield Stress and Ultimate Tensile Strength, all three samples exceeded the minimum mechanical properties to meet ASTM A182 F22 steel.