Evaluation of the effect of boride layer structure on the high temperature wear behavior of borided steels

The present study evaluates the high temperature sliding wear characteristics of the paste borided 31CrMoV9 and X40CrMoV5-1 steels with respect to the phase structure of the boride layers. Boride layers formed on the surfaces of the examined steels were about 65μm in thickness and consisted of FeB and Fe₂B phases. The volume fraction of FeB (V_FeB) in the boride layers were 31% and 47% for 31CrMoV9 and X40CrMoV5-1 steels, respectively. The testing temperature of 500°C caused an increment in the wear loss and the friction coefficient for both of the borided steels while their tribological performances were almost similar at room temperature (RT). In association with the presence of low amount of V_FeB in its boride layer, borided 31CrMoV9 steel underwent severe wear at 500°C as the result of heavy cracking on the worn surface when compared to the borided X40CrMoV5-1 steel.