FeB和Fe_2B价电子结构与钢表面渗硼层硬化本质

Valence Electron Structures of FeB and Fe_2B and the Hardening Essence of Boronizing Layer of Steel Surface

依据EET理论,计算了FeB和Fe_2B价电子结构并分析了它们与钢渗硼层硬化的关系。研究发现:渗硼表面改性后,钢表面硬度和耐磨性提高的根本原因在于FeB和Fe_2B最强键的键合力远大于基体α-Fe最强键的键合力;FeB的硬度比Fe_2B大的微观本质在于FeB相最强键的键合力、主键络连接键的键合力和共价电子密度分别比Fe_2B的大27.12%、4.8%和3.66%;FeB相比Fe_2B脆性大的微观本质在于FeB共价键空间分布更不均匀,FeB相主键络具有较强的共价性,而Fe_2B相主键络具有较强的金属性;由于FeB相成键能力仅比Fe_2B的成键能力大0.85%,因此优先形成的Fe_2B相极易转变为FeB相,使得钢表面渗硼层的脆性增强。

Based on the empirical electron theory of solids and molecules(EET),the valence electron structures(VESs)of FeB and Fe 2B were calculated,and then the relationship between them and hardening in boronizing layer of steel surface was analyzed.It is showed that after boronizing,the basic reason of the increase of hardness and abrasive resistance in steel surface lies in the binding forces of the strongest bond of FeB and Fe 2B are far bigger than that ofα-Fe in matrix.The hardness of FeB is bigger than that of Fe 2B,which microscopic essence lies in the binding force of the strongest bond,the binding force of the main bond structure connection and the covalence density in FeB is 27.12%,4.8%and 3.66%bigger than that of Fe 2B respectively.Compared with Fe 2B,the covalence bond space distribution is more nonuniform of FeB while its main bond structure has stronger covalence but that of Fe 2B has stronger metallicity,which is the basic reason that brittleness of FeB is bigger than that of Fe 2B.The bonding power of FeB is only bigger than that of Fe 2B 0.85%,so Fe 2B priority to formed easily changes to FeB and lead to the brittleness increase in boronizing layer of steel surface.