High Temperature Friction and Wear Property of Hot Stamping Tool Steel SDCM

The high temperature friction and wear properties of a new kind of hot stamping die material, SDCM steel, were investigated on a UMT-3 high temperature friction and wear tester using a high quality hot work die material, CR7V steel, as a benchmark. The microstructure and oxidation resistance of SDCM after heat treatment, morphologies and composition of the worn surface and cross-sectioned worn surface at eldevatd temperature were determined by using scanning electron microscope, transmission electron microscopy, X-ray diffraction analysis, Bruker white light scanning profiler. Results indicate that wear mechanisms of SDCM steel were different at elevated temperature. Adhesive wear dominated at 100℃. Mild oxidation wear and adhesive wear were observed at 300℃ and 500℃. The dominate wear mechanism was oxidation wear at 700℃. At temperatures from 100℃ to 400℃, CR7V exhibited high wear resistance due to the presence of M₂₃C₆ and M₇C₃ carbide, which were for 3.4% and 12.7% of the total carbide, respectively. From 500℃ to 700℃, SDCM had high resistance to temper softening. In addition, it had poor resistance to oxidation because of the low quantity of Cr. As the result, the tribo-oxide layer on the worn surface acted as a "lubricant" and responsible for the high wear resistance of material at 700℃.