Abstract:Steel T8 treated by plasma surface decarburizing was alloyed by the Xu-Tec process with Co,W and Mo. An alloyed layer of Fe-Co-W-Mo with low carbon content was formed on the surface of the high carbon steel, thus an advanced gradient composite was produced. The specimens then were treated by the solution and aging treatments. The characteristics of age-hardening of the alloying layer were studied. The hardness of the surface layer increases from HV200 to HV1 200 after the solution treatment at 1190℃and aging at 400℃for 30min. The results show that the surface aged high speed steel possesses not only high surface hardness, but also enough bulk strength.

Key words: high carbon steel; plasma decarburizing; age-hardening; surface aged hardening alloy