The effect of chromium and CrB_2 additions on the formation of borides during laser surface modification of steel

摘要

The addition of varying amounts of chromium along with CrB_2 to 4340 steel during laser surface alloying produces surfaces with enhanced hardness, wear resistance and (for some combinations) improved corrosion resistance. The hardness and wear resistance increased linearly with the increase in CrB_2 additions indicating radual changes in phase content. Most of the CrB_2 dissociated in the melt and reformed as other compounds. The resulting compounds after recombination during solidification were CrB_2, CrB, and (Fe,Cr)_2B. Improved corrosion resistance resulted when the ratio of chromium to CrB_2 in the precursor was 1:1 or larger. The presence of the chromium additions also influenced the boride phases which formed.