| Title |
Secondary Hardening and Fracture Behavior in the Co and Cr Bearing W and Mo Steels |
| Authors |
이건배(Kon Bae Lee) ; 양형렬(Heong Ryeal Yang) ; 권훈(Hoon Kwon) |
| Abstract |
In alloy systems of the WCrCo and MoCrCo steels, the secondary hardening and fracture behavior were studied. The decrease in hardness was very small up to 500℃ tempering temperature before the Co addition led to the clear secondary hardening at 550℃. Also, the peak hardness was higher than the as-quenched hardness. Since the Co addition may increase the driving force for formation of the M₂C type carbides and inhibit the softening by delaying the recovery of the dislocation structure, a substantial secondary hardening can be produced by the fine precipitation of M₂C type carbides from such a dislocation structure. The Co addition may degrade the impact toughness by means of the lowering of intrinsic toughness of matrix, the precipitation hardening of M₂C type carbides and the retention of coarse cementite. In the WCrCo steel, the lower hardeness and the higher impact toughness at relatively high test temperatures may result from the less dense precipitation of M₂C type carbides. |