Experiments and simulation of rapid solidification of air plasma sprayed alloy 625 on stainless steel

There is growing interest in the use of superalloy coatings to improve the high temperature properties of base materials. Thermal spraying methods such as air plasma spraying (APS) are convenient techniques to deposit such coatings. This work examines the rapid solidification of APS deposited alloy 625. While conventionally processed materials solidify near the equilibrium temperature, in the case of plasma sprayed alloy 625, non-equilibrium effects during the rapid solidification of a molten particle must be taken into account. The model presented here solves the equations for heat and mass transfer to predict the interface undercooling and velocity as a function of time. Non-equilibrium behavior near the solid/liquid interface plays an important role in determining the morphology of the solidification front, and so the microstructural characteristics of rapidly solidified alloy 625 are also predicted, as a function of interface velocity. The results are compared to those obtained from experimental data of the microstructure of alloy 625 splats.