Ni-20Cr-Nb-W 系合金の高温クリープ特性に及ぼす粒界析出相の効果

概要

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Creep properties and microstructure of Ni-20Cr-Nb-W alloys containing variable amounts of niobium and tungsten were investigated at 900 and 1000℃, focusing on a role of grain boundary precipitates. The alloys with higher niobium content, in which the Widmanstatten type β-Ni_3Nb phase precipitates after its precipitation at grain boundaries, showed a relatively small minimum creep rate at 900℃ accompanied by the degradation of rupture elongation. The effect of the time lag between the in-grain and grain boundary precipitations of the β-phase on the creep resistance of the alloys was evaluated by observing their creep rate-time curves. When the tungsten content of a Ni-20Cr-3Nb-13W alloy increased up to 17 wt%, marked improvement of creep properties was found under lower stress levels and it is strongly correlated to the grain boundary precipitation of the α_2W-phase which occurs after that of the β-phase. It is concluded that the grain boundary precipitation strengthening effect due to such dual phases as β and α_2 is one of most effective methods for improving the creep strength.
社団法人日本鉄鋼協会の論文
1986-08-01