Effects of HFMI Treatment on the Boron-Alloyed Austenite Medium-Manganese Steel 140Mn6Cr3TiB Deposit: Enhanced Wear Resistance Induced by Heterogeneous Microstructure

This paper aims to analyse the microstructure and properties of the titanium- and boron-alloyed high-carbon medium-manganese 140Mn6Cr3TiB steel deposit before and after high-frequency mechanical impact (HFMI) treatment. XRD, SED, and EDS analyses were applied to evaluate the microstructural peculiarities of the studied deposit. Nanoindentation and scratch/sliding tests respectively revealed distinct correlations between the phase composition and the deformation/wear behaviour. HFMI results in the formation of the strain-induced ε- and α’-martensites (~66% and 3–6%, respectively), a significant grains/crystallites refinement (down to 31–54 nm), and dislocation density, which support essential hardening (by ~50%). The HFMI regime (load = 100 N, amplitude = 10 µm, and time = 60 s) was found to be the best, which led to the enhanced wear resistance (decreased wear volume) by ~4 times. The heterogeneous nature of the steel deposit creates a “shield-and-buffer” effect, where the hard eutectic framework resists penetration and tough matrix prevents brittle failure, maintaining a high tolerance to abrasion damage. The HFMI-hardening changed the wear mechanism from the ‘wedge/pile-up’ formation to ploughing. Thus, the HFMI shows a good efficiency in finishing the protective medium-manganese steel deposits of enhanced wear resistance to prolong the operation life of responsible parts.