Friction Behavior and Self-Lubricating Mechanism of SLD-MAGIC Cold Worked Die Steel during Different Wear Conditions

Abstract

Wear tends to shorten tool life, reduce component quality. To prevent or postpone the wear of tool steel forming tools, methods to increase wear resistance, such as increasing the material hardness, optimizing the carbide distribution and application of surface coatings, are often used. However, the formation of lubricating phases in steels leading to anti-attrition is less investigated. The friction behavior of three steels were investigated thoroughly by a tribo test with different normal loads. A Field-emission scanning electron microscope (FE-SEM) along with energy dispersive X-ray spectroscopy (EDS) were used to characterize the microstructure as well as the influence of the precipitated phases on the wear mechanisms. Results showed the friction coefficient decreased with increasing normal load, whereas the wear rate increased with increasing normal load. Compared with SKD11 and DC53 steels, the friction coefficient and wear volume of SLD-MAGIC steel were reduced by 0.1 to 0.3 and 10% to 30%, respectively. With the increase of normal load, the wear mechanism changed in order from abrasive wear, adhesive wear to oxidation wear. The more carbide contents, the rounder the carbide, the better the wear resistance of the tool steel. It can be shown that, under different normal loads, SLD-MAGIC exhibits better wear performance than SKD11 and DC53 tool steels, which is mainly due to the self-lubricating phenomenon of SLD-MAGIC steel. The self-lubricating mechanism was due to the fact that the exfoliated sulfide during wear formed a lubricating film to reduce wear.