Not absolutely sure if it is Carbon Steel. It's molded or sandwiched into the carbon steel. I put on the grinder and it made vary few sparks and probably mostly from the surrounding carbon steel. The hardened material appears to be molded into the steel by 1/2" X 1/2" strips side by side. The face side or wear side of the edge has been warn back to reveal the hardened material about 2/3 the way Back into the steel Thanks