Kinetic study on NaF-activated pack-aluminizing of pure titanium at 950-1100 °C
(1. Centre of Excellence for High Strength Alloys Technology, School of Metallurgy and Materials Engineering,
Iran University of Science and Technology, Narmak, Tehran 168463114, Iran;
2. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China)
Iran University of Science and Technology, Narmak, Tehran 168463114, Iran;
2. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China)
Abstract: Pure titanium samples were aluminized at 950, 1025 and 1100 °C for 0-6 h in a pack containing 10%Al+5%NaF+ 85%Al2O3 in mass fraction. The aluminized layers formed on the samples were characterized. The kinetic studies indicated that the diffusion of Al-bearing gases through the pack is the rate-controlling step in this process. The activation energy of 161.8 kJ/mol was calculated for this step. In addition, the mass gains of the aluminized samples were predicted using the partial pressures of gases in the pack and those adjacent to the samples surface. The predicted values are in good agreement with the experimental measurements at 950 ？C but are higher than those measured at 1025 and 1100 °C.
Key words: pack aluminizing; titanium aluminizing; aluminizing kinetics; titanium aluminides