Kinetic study of boron diffusion in a γ-TiAl intermetallic alloy using the pack-boronising method

Boronising is a thermochemical treatment which enhances the resistivity of metals used as component in applications dominated by wear and corrosion. In this study, boronising was performed on a gamma-TiAl intermetallic alloy with the pack cementation method. The experiments took place at temperatures 1173-1323 K for 8-14 h and a compact hard boride layer was formed. Its thickness varied between 6 and 25 mu m. An 80 mu m wide boron diffusion zone with elevated hardness was detected via micro-hardness measurements. The measured thickness values were applied to a mathematical model based on Fick's second law of diffusion to extract the kinetic parameters of the process. Additionally, the presence of the tau i Beta(2) and the total absence of the TiB phase were confirmed via XRD measurements. The hardness of the coating and the substrate was evaluated using Vickers micro-hardness tester (above 1100 HV at the coating layer).