粉末冶金法による Ni 基合金の高温引張特性に及ぼす熱処理条件の影響

概要

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A study was made on effects of conditions of heat treatment on tensile properties at 760℃ for HIP-consolidated powder of a Ni-base superalloy with a designed γ'-phase content of 65%. The heat treatment comprised two or three stages : solutionizing, (intermediate heat treatment), and aging. Experimental Yield-Strength (YS) and Ultimate-Tensile-Strength (UTS) were classified into two levels, depending on the conditions of heat treatment. The classification matched well with the difference of size of γ'-phase. Gamma-prime phase was fine and experimental YS and UTS were high, when cooling after solutionizing was rapid, or when an intermediate heat treatment at comparatively high temperature was applied. The reverses were the case when the rate of the cooling or the temperature of the intermediate heat treatment was reversed. Rupture elongation significantly varied depending on the conditions of heat treatment. The variation, however, was not accounted for by change of structure. Elongation was large when cooling after solutionizing was slow, while it was small when solutionizing was prolonged, when cooling after it was rapid, or when an intermediate treatment was applied. The best performance was obtained when a specimen was solutionized for 1 h and air-cooled thereafter, followed by aging without intermediate treatment.
1989-05-01