Diffusion kinetics of borided of low entropy soft magnetic FeCo alloy

Abstract

The growth kinetics of boride layers were investigated by boronizing the FeCo low entropy alloy produced by arc melting reverse vacuum system with the pack boriding method at temperatures of 1173 K, 1223 K, 1273 K and for 2, 4, 6 h. FeCo alloy has a single-phase FCC crystal structure and there are linear cracks and homogeneously distributed point voids in its microstructure. The hardness of FeCo alloy is between 170 HV0.05 and 265 HV0.05. The boride layer appearance has a sawtooth appearance, and the layer thickness varies between 62 µm and 172 µm depending on temperature and time. According to the XRD pattern, (CoFe)B and (CoFe)B2 triple phases are present on the boride layer surface. With pack boriding, the hardness of the boride layer increased up to 2262 HV0.05, and the surface hardness of the alloy improved by 8–10 times. The boride layer activation energy of the FeCo alloy boronized with pack boriding was calculated as 89.065 kJ mol−1.