The boride layer was fabricated on the surface of carbon steel by a novel RE-Chrome-Boronizing technology assisted by fast multiple rotation rolling (FMRR) treatment at low temperature. The microstructure of the boride layer was characterized by using scanning electron microscopy (SEM). The microstructure of the top surface layer of substrate was characterized by transmission electron microscopy (TEM) and high resolution rransmission electron microscopy (HRTEM). Experimental results showed that a nanostructured layer with grain size of approximately 30 nm was obtained; the amorphous phase and high-density dislocations were observed in upper-layer of FMRR samples, which led to the reduction of diffusion activation energy of boron atoms. Boride layers fabricated on the FMRR samples are continuous, dense, uniform, and low in brittleness. The penetrating rate was enhanced significantly when the FMRR samples were Cr-Rare earth-boronized at 650 degrees C for 6 h. The thickness of the boride layer of FMRR samples on carbon steel was approximately 25 pin when the duration was 60 min, which was approximately 1.5 times higher than the original sample. The boride layer consisted of mainly Fe2B, and adheres well to the metallic substrate. (C) 2015 Elsevier B.V. All rights reserved.