Microstructure evolution and mechanical properties of high-boron steel with different ratios of boron and carbon

Boron and carbon contents are the main factors influencing the properties of high-boron steel. In this study, experimental samples with different boron-to-carbon ratios (%B/%C) were prepared. The microstructures of the different samples were observed, and their hardness, bending strength, and impact toughness were investigated. Results show that the main microstructures in the investigated high-boron steel samples are the eutectic Fe₂B structure with a fishbone shape and the ternary peritectic Fe₃(C, B) structure with a chrysanthemum shape. When the boron content is 2.5wt.% and the carbon content is 0.43wt.% (i.e., %B/%C=5.82), the overall mechanical properties of the alloy are the best. The alloy’s hardness, bending strength and impact toughness reach their maximums, which are 67.3 HRC, 1,267.36 MPa and 6.19 J·cm^-2, respectively. The optimized alloy is compared with conventional materials exhibiting excellent wear resistance (namely, high-manganese steel and high-chromium cast iron) through two-body and three-body abrasion tests. The wear resistance of this high-boron steelinvestigated in this work is found to be superior to those of the more common materials.