A study of the behavior of boron diffusion in plain carbon steels

Boronizing treatment of ferrous materials has been widely employed by industry as a surface-strengthening technology for inhibition of corrosion, wear and erosion. Pack boronization using a pack composition that produces a graded boride microstructure has been studied using AISI 1018 and 1045 steels. Carbon in these alloys creates a resistance to boron diffusion because a carbon-enriched zone forms in front of the boride layen The carbon concentration at the boride/pearlite interface was found to be as high as 3.0% in AISI 1045 steel. No significant layer phenomena could be distinguished inside the boron layer using the pack composition developed during this research. This result is significant because a graded microstructure with a continuous variation of the boron composition has been produced. Evidence developed during this study suggests that the boride layer consists of a mixture of FeB, Fe₂B, and FeB_x, which is probably FeB₁₉. Analysis determined a measure of the resistance of carbon to boron diffusion at the boride/pearlite interface.