Mechanically polished steel (1H18N9T) and (15GTM) samples are implanted with boron, titanium, and nitrogen ions, with dose ranging from 1016 to 1017 ions/cm2. The implantation energy varied from 100 to 250 keV. Implanted samples are heat‐treated at 400 to 800 °C in vacuum. The microhardness of implanted samples is measured by using a Hanneman tester with loads ranging from 2 to 40 g. The influence of annealing temperature on microhardness of the implanted layers is determined. The diffusion of boron from the implanted layers is also investigated by using the secondary ion mass spectrometer. The diffusion coefficients of boron in steel are determined.