Grade 91 steel is used in the nuclear industry for its excellent strength, creep resistance, and radiation tolerance. Directed energy deposition (DED) is a potentially attractive method to manufacture Grade 91 steel components for the nuclear power industry. Structurally sound and reliable parts made by DED require selection of appropriate process conditions to achieve superior microstructure and properties. Components experience repeated thermal cycles when previously formed martensitic structure undergoes in-situ tempering. Careful selection of processing conditions such as laser power, scanning speed, powder mass flow rate, and preheat temperature is important for tuning the thermal cycles responsible for the tempering. The main objective of this work is to combine the thermal cycles calculated using a mechanistic model with appropriate phase transformation kinetics to quantitatively compute the extent of tempering of Grade 91 steel components for different processing conditions. More details are available in the following paper.
T. Mukherjee, T. DebRoy, T.J. Lienert, S.A. Maloy, P. Hosemann, Spatial and temporal variation of hardness of a printed steel part, Acta Materialia, 2021, vol. 209, article # 116775.
