高効率ガスタービン用Ni基超合金のクリープ条件下でのき裂形劣化挙動

概要

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In order to clarify a crack type degradation mechanism of a directionally solidified Ni-base superalloy CM 247 LC, the effects of environment and microstructural changes on the crack initiation and growth behavior under creep condition have been investigated using an optical and scanning electron microscopes. Metallographic examinations revealed that the surface crack initiation and growth were closely associated with the internal oxidation, nitriding and decomposition of grain boundary carbides. The surface crack initiated at AIN/γ-matrix interface and propagated along a γ′ and carbide-free grain boundary. It was also found that the grain boundary M_23C_6 carbide was preferential site for creep cavity initiation, and the transformation of M_6C to M_23C_6 during creep was the critical factor of the internal crack type degradation. Furthermore, the transgranular cracking occurred primarily along the γ-channel, which became lamellar constituent perpendicular to the loading direction because of the raft structure formation.
一般社団法人日本機械学会の論文
2001-02-25