Ni-Mo-Cr foams processed by casting replication of sodium aluminate preforms

The use of sodium aluminate (NaAlO₂) for casting Ni-based alloy foam using the replication method, was analyzed. The creation of Ni-based superalloy foams by casting replication requires a space-holder materials with high melting point and chemical inertness with the melt. Sodium aluminate exhibits a melting point (1650°C) that suits the replication process. It showed moderate melting point, which prevent melting at the infiltration temperature and allow sintering of a preform with relatively coarse powders. It was also found to be lightly sintered to one other without reaction with the alumina crucible. The casting method was used to create a foam from the nickel-base alloy. Sodium aluminate was infiltrated at low pressure, where its phase was removed by dissolution in a 10% HCI solution, producing nickel-base foam with relative density of 46%.