Boronizing of iron aluminide Fe72Al28

Boronizing of Fe72Al28 was carried out in a slurry salt bath composed of borax and SiC at temperatures between 900 and 1050 °C for different durations starting from 3 h up to 15 h. The microstructures and microhardness of boride layers and intermetallic matrix were analysed. Samples boronized had Fe2B phase or Fe2B plus FeB phases depending on the process temperatures and times. SEM-EDS studies indicated that there was major aluminium migration into the matrix leaving only 3-4 at.% aluminium in the boronized layer. The measured microhardness values of the boronized layers varied from 1014 to 1980 HV and their thickness increased from 13 up to 103 μm with increasing temperature and processing times. The kinetics of the boronizing reaction have been analysed and the controlling diffusion process determined.