On the Influence of Aluminum and Carbon on Abrasion Resistance of High Manganese Steels

Abrasive wear testing of lightweight, austenitic Fe-Mn-Al-C cast steel has been performed in accordance with ASTM G65 using a dry sand, rubber wheel, abrasion testing apparatus. Testing was conducted on a series of Fe-30Mn-XA1-YC-1Si-0.5Mo steels containing aluminum levels from 2.9 to 9.5wt% and carbon levels from 0.9 to 1.83wt%. Solution treated materials having an austenitic microstructure produced the highest wear resistance. Wear resistance decreased with higher aluminum, lower carbon and higher hardness after age hardening. In the solution treated condition, the wear rate was a strong function of the aluminum to carbon ratio and the wear rate increased with a parabolic dependence upon the AUC ratio, which ranged from 1.8 to 10.2. Examination of the surface wear scar revealed a mechanism of plowing during abrasion testing and this method of material removal is sensitive to work hardening rate. Work hardening rate was determined from tensile tests and also decreased with increasing Al/C ratio and after aging hardening. The loss of wear resistance is related to short range ordering of Al and C in the solution treated materials and K-carbide precipitation in age hardened materials. Both short range ordering and K-carbide precipitation contribute to planar slip and lower work hardening rates. A high carbon tool steel (W1) and a bainitic low alloy steel (SAE 8620) were also tested. A lightweight steel containing 6.5wt% Al and 1.2wt.% C has wear resistance comparable to within 5% of the bainitic Society of Automotive Engineers (SAE) 8620 steel forging currently used for the Bradley Fighting Vehicle track shoe and this cast Fe-Mn-Al-C steel, at equivalent tensile properties, would be 10% lighter.