Understanding the formation process of shrinkage pores with a 3D dendrite growth model: from casting to additive manufacturing

A three dimensional dendrite growth model is used to investigate the formation of shrinkage pores in nickel-based superalloy during the solidification process. A variety of simulations are performed with the temperature gradients and cooling rates under the casting and additive manufacturing conditions. The shrinkage pores are identified according to the localized liquid feeding condition. The investigation on casting not only validates the current model and methodology by comparing with a published X-ray imaging result but also uncovers more critical details, including the location preferences of shrinkage pores in the dendrite structure and the formation sequences of shrinkage pores in different stages, which have never been revealed in available literatures. After that, the effect of cooling rate on the pore formation is discussed for different mechanisms. In the investigation of additive manufacturing, the formation mechanisms of shrinkage pores are identified and well explain the shrinkage pores found in experimental results. Furthermore, the effects of the cooling rate and the new phases on the formation of shrinkage pores are discussed.