TEM OBSERVATION OF NUCLEATION AND GROWTH OF BORIDE DURING BORONIZATION OF STEEL 20 AND INFLUENCE OF PRIOR DEFORMATION

The TEM observation on the single-side thinned specimens was made of the nucleation and growth of boride during boronization for steel 20 and the influence of prior room temperature deformation.The results of X-ray diffraction and electron probe microstructure analysis show that only Fe_2B formed in the surface layer of specimens at the beginning of boronization;the atomic concentration of B in the surface layer increased with the increase of deformation monotonously;and the segregation of B atoms in the dislocation cells hindered the recovery and recrystallization of the deformed structure of the matrix and accelerated the nucleation and growth of boride in the surface layer.