Application of the Heat Balance Integral Method to the growth kinetics of nickel boride layers on an Inconel 718 superalloy

New results about the growth kinetics of nickel boride layers on an Inconel 718 superalloy were obtained. The nickel boride layers were developed by means of the powder-pack bonding process at 1173-1223 K with different exposure times for each temperature. According to optical and scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and nanoindentation techniques, the microstructure of the boride layer consisted in three zones: a high content of Ni4B3 on the outer-zone of the bonded surface, while Ni2B and Ni3B were revealed at the inner zone of the layer and diffusion zone, respectively. Moreover, the bonding growth kinetics of nickel boride layers was estimated using the Heat Balance Integral Method (HBIM) based on a numerical resolution of a system formed by differential algebraic equations, and considering that the evolution of the layers is governed by the parabolic growth law. For the range of bonding temperatures, the boron activation energies in the Ni4B3, Ni2B and Ni3B resulted in 233, 206 and 218 kJ mol(-1), respectively.

Automated summary

New results on the growth kinetics of nickel boride layers on Inconel 718 superalloy were obtained through powder-pack bonding process at different temperatures. The microstructure of the boride layer was found to consist of three zones, and the bonding growth kinetics of nickel boride layers were estimated using the Heat Balance Integral Method (HBIM). Activation energies for boron in Ni4B3, Ni2B, and Ni3B were determined to be 233, 206, and 218 kJ mol(-1), respectively.