The effect of doping with copper and aluminum on structure, mechanical and friction properties of steel

The influence of copper on the structure, mechanical and friction properties of 1.5% aluminum-doped steel with 0.3% carbon was studied. It was revealed that there are macro- and nano-sized copper-containing inclusions, that is confirmed by optical microscopy and TEM. According to the results of roentgen-phase analysis, these phases are on the basis of a solid solution of copper. It was found that the increase in copper concentration from 1.66 to 7.37% leads to a decrease in the size of the ferrite grains by 4 times and increase the level of microhardness of pearlite and ferrite in 1.5. When concentration of copper in the steel increases due to the growth of nanoscale copper inclusions, friction ratio decreases, that improves frictional properties of steel. Increase of macro sized copper-containing inclusions reduces friction ratio at loads less than 4 MPa, and increases at high loads, which negatively affects the friction properties of steel.