Ni-Cr-W 系合金の組織とクリープ破断強度におよぼす Cr-W バランスと C 量の影響(高温の組織と強度)(<特集>耐熱鋼・耐熱合金)

概要

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In order to determine the practically optimum composition in an Ni-Cr-W austenitic alloy system for an intermediate heat exchanger of a high temperature gas cooled reactor, the effects of Cr-W balance and carbon content on the struture and creep rupture strength in the alloy system have been investigated. Austenite single phase region determined by experiment is much smaller than that calculated by Barrows method in Ni-Cr-W system at 1000℃. Outside the austenite single phase region α-W and at least one of M_6C and M_<23>C_6 carbides precipitate depending on the Cr-W balance. The precipitation of α-W and M_<23>C_6 carbide improves creep rupture strength, but that of M_6C carbide rather degrades it, although solid solution strengthening is maximized at a Cr-W balance in the M_6C predominant region. Among the alloys investigated in this study the 0.05%C-23%Cr-18%W-Ni alloy which is strengthened through the precipitation of M_<23>C_6 carbide and about 3% of α-W is the best from the point of view of creep rupture strength. For the carbon content of the above mentioned alloy the range from 0.040% to 0.065% is practically optimum, because excessive carbon causes M_6C carbide precipitation and degrades creep rupture strength.
社団法人日本鉄鋼協会の論文
1979-06-01