20Ni-28Cr-Co-Fe系耐熱鋳造合金の高温クリープ強度に及ぼす合金元素の影響

概要

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The heat resistant alloy based on 30%Cr-50%Co-Fe has been cast into skid rails of furnaces until now. It is an expensive one and comes short of the strength at elevated temperatures above 1100°C. In order to design a new alloy replacing it, the strengthening factors of alloying elements were evaluated for the 1100°C, 100h creep rupture strength of a cast alloy with 20Ni-28Cr-Co-Fe containing 10 to 37%Co, max 5%W, max 0.8%Mo, max 1.4%Nb and max 0.17% (C+N).The results are as follows.(1) All of alloying elements enhanced the strength. The strengthening factors in MPa/at%, of Nb, W, C+N, Mo and Co are 3.3, 1.76, 1.40, 0.35 and 0.0125 respectively.(2) The elements of smaller diffusion coefficients are more effective to strengthen the alloy at elevated temperatures.(3) Therefore the alloy containing less Co and adequate Nb and/or W is to be stronger and also less expensive.
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