| 摘要 |
PURPOSE:To enhance the resistance to erosion and seizure, by making one valve contact surface of a cobalt-based Co-Cr-W alloy, and another valve contact surface of a nickel-based alloy of 400 or more in hardness (Hv). CONSTITUTION:The contact surface of one of a valve casing and a valve element is made of a cobalt-based Co-Cr-W alloy, while that of the other is made of a nickel-based alloy or an iron-based eduction-hardened alloy, which has a hardness (Hv) of 400 or more. For example, Stellite 3, 6, 21 or 25 is used as the cobalt-based Co-Cr-W alloy. For example, an Ni-Cr-Mo-Nb alloy, an Ni-Cr-Al-Mo alloy or an Ni-Cr-B-Si-C-Fe alloy is used as the nickel-based alloy of 400 or more in hardness (Hv).
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