| In alloy systems of the WCr and MoCr steels, which contains both the W or Mo, M₂C type carbide forming elements, and the Cr, the secondary hardening and fracture behavior were studied. The extent of secondary hardening was very weakened and the secondary hardening temperature range was lowered in the MoCr steel, as compared to the ternary Mo steels. Furthermore, the secondary hardening did not occur in the WCr steel. Because the Cr addition stabilizes the cementite of M₃C type, the effective precipitation of fine M₂C carbides cannot be achieved. In the WCr steel the coarse cementite is retained at higher temperatures probably due to the additive stabilizing effect of the W. Although the Cr addition has no merit in the secondary hardening itself, however, it eliminated the secondary hardening embrittlement, which was observed in the Mo and W steels in the absence of Cr. |
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