Abstract: On the basis of Yu’s empirical electron theory of solids and molecules， the valence electron structures of Fe2B phase and Cr-containing Fe2B phase (known as boride layers) are researched. At the same time， the effect on decreasing the eigen-brittleness of the boride layer， by pack RE-chrome-boronizing， on its friction and wear behavior is studied using an MM—200 wear tester. Compared with that of Fe2B phase， the valence electron structure of Cr-containing Fe2B phase has been changed， which results in the improvement of the eigen-brittleness of the boride layer and the enhancement of the weak bond B—B in the Fe2B phase. The drop of eigen-brittleness of boride layer can increase its load bearing capacity， wear resistance and friction-reducing. The friction and wear mechanism of the boride layers is too analyzed.

Key words: Boride layer, Eigen-brittleness, Friction and wear, RE-chrome-boronizing, Valence electron structure