Effect of Mechanical Alloying on Pack Boronizing

Abstract

Abstract In this study, the effect of mechanical alloying on the growth kinetics of boride layer of boronized DIN St28 steel surface was investigated. The powders containing B + SiC + KBF4 were mechanically alloyed by planetary ball milling devices to 10 and 20 h, respectively. The samples were also boronized by the powder-(SiO2–Na2O) mixture for 1023–1173 K temperature and 3, 6 and 12 h, respectively. At the end of the mechanical alloying process, it was determined that the powder particle sizes were in the nanometer scale. According to the microstructure analysis, a single-layer Fe2B structure was successfully obtained on the samples surfaces. It has been observed that the depth of the Fe2B boride layer, which has achieved high diffusivity by creating many defects in the form of nanometer-sized crystal particles, increased with repeated fracture and cold welding of the powder particles with increasing mechanical alloying times. By calculating the activation energies of the powders, their relations with the mechanically unalloyed samples were compared and empirical formulas that could be used for similar experimental conditions were produced.