NiおよびCo基鋳造合金の高温低サイクル疲労強度と静的強度の温度依存性の相関について

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The correlation between tensile strength and low cycle ftigue life at elevated temperatures was discussed on a cast Ni base supper alloy (16Cr-3Al-3Ti-9Co-Ni) and a Co base super alloy (11Ni-29Cr-7W-Co). Also,an equation for predicting low cycle fatigue life was developed. In the low cycle fatigue tests, the Co base super alloy showed similar fracture behavior in a wide range of temperature. However, the Ni base super alloy showed brittle fracture behavior at low temperatures (ex. 500℃) because of poor ductility, but showed ductile fracture behavior at low temperatures (ex. 900℃) because of high ductility. In the Ni base super alloy, the failure life was fefined as the number of cycles when the nominal stress value of a specimen began to decrease from a steady state stress. Tensile and low cycle fatigue data obtained at 500-900℃ for the Ni base super alloy and 600-900℃ for the Co base super alloy were analyzed by the stepwise multiple regression precedure, and the effect of tensile strength characteristics on the low cycle fatigue strength was discussed. The results of this analysis showed that the relationship between the plastic strain range (Δε_p) and cycles to failure (Ν_f) was expressed by a functin of ε_f, while the relationships between the elastic strain range (Δε_e) and cycles to failure was given by a functin of (σ_<0.2>/Ε) for both super alloys in a wide range of high temperatures, unlike the results of the Universal Slope method. The life prediction equation obtained was as follows: Δε=Δε_e+Δε_p=A(σ_<0.2>/Ε)^lΝ^k_f+Βε^n_fΝ^m_f where Α, Β, k, l, m and n are material constants that are independent of temperature.
1989-09-15

NiおよびCo基鋳造合金の高温低サイクル疲労強度と静的強度の温度依存性の相関について

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