Residual stresses and microstructure of H13 steel formed by combining two different direct fabrication methods

Direct fabrication techniques can be combined to produce composite DF specimens, with spray-forming rapidly building up the base material for die-surface features and backing, and Laser Engineered Net Shaping (LENS) creating the other final-surface or fine-detail features. Residual stresses are lower, and the microstructural "processing zone" that marks the transition between the characteristic structure of each native DF process is narrower, for LENS deposited directly on the final as-spray-formed surface instead of a mechanically polished surface. Stress-relief of the spray-formed H-13 steel prior to additional LENS processing may also lower the residual stresses across the transition interface. Very large residual stresses can exist in H-13 steel across the interface between the two inherently different DF processes. However, proper characterization feedback should allow surface preparation and heat-treatment parameters to be chosen which minimize such stresses.