Effect of Carbon Content on Microstructure and Properties of Cr25 High-Chromium Cast Steel

The effects of carbon content (0.13wt%, 0.25wt% and 0.32wt%) on the microstructure, high-temperature oxidation resistance and high-temperature wear resistance of Cr25 high-chromium cast steel were investigated. The results show that the microstructures of the cast steels with different carbon content are composed of ferrite matrix and (Cr ·Fe)₂₃C₆ carbide. The morphology of carbides changes from discontinuous rod-like to continuous net-like, and the precipitation way changes from intergranular to intergranular and intragranular precipitation. In the early stage of oxidation at 1 200 ℃, the tested steel is oxidizing rapidly. After oxidation for 40 h, the oxidation rate tends to remain stable and the tested steel is in a stable oxidation stage due to the chromium oxide protective layer formed on the surface. With the increase of carbon content, the high-temperature oxidation resistance of the tested steel decreases while the wear resistance increases, and the wear mechanism changes from adhesive wear to the combining of adhesive and abrasive wear.