Distribution of Phosphorus and Its Effects on Precipitation Behaviors and Tensile Properties of IN718C Cast Superalloy

doi:10.1007/s40195-018-0834-1

摘要/Abstract

关键词: IN718C alloy, Phosphorus, γ″ and γ′ phases;, δ phase;, Tensile properties

Abstract:

The effect of phosphorus on the precipitations of γ″, γ′ and δ phases and associated tensile properties in IN718C alloy are investigated in this study. It is revealed that P atoms are dissolved in the grain interior to a relatively high degree and hence influence the precipitation behaviors in the grain interior and improve the tensile strength of IN718C alloy. γ″ and γ′ phases did not precipitate in the alloy without P addition during air cooling, while γ″ and γ′ phases precipitated in the grain interior during air cooling in the alloys with P addition, and the amounts of γ″ and γ′ phases increased with increasing P content. Therefore, the Vickers micro-hardness in the as-cast state increased gradually with increasing P content. In double-aging state, the sizes of γ″ and γ′ phases in the alloys with P addition were larger than that in the alloy without P addition, while the sizes were invariable when the P content (wt%) was higher than 0.015. Therefore, the micro-hardness and tensile strength of IN718C alloy treated by double aging increased first and then kept invariable with increasing P content. The precipitations of δ phases both in the grain interior and on grain boundaries were inhibited by P markedly. The inhibitory effect of P on δ phase enhanced gradually with increasing content of P, but the plasticity increased first and then decreased. What is more, the crack tended to propagate into the matrix around the particles (Laves phases and NbC carbides) in the alloys without P addition at the beginning of the tensile fracture, while it tended to propagate along the interfaces between the matrix and those particles in the alloys with P addition, which resulted from the synthetical effect of P on γ″, γ′ and δ phases.

Key words: IN718C alloy, Phosphorus, γ″ and γ′ phases;, δ phase;, Tensile properties

. [J]. Acta Metallurgica Sinica (English Letters), 2019, 32(7): 887-899.

An-Wen Zhang, Yan Yang, Sha Zhang, Dong Zhang, Wei-Hong Zhang, Da-Wei Han, Feng Qi, Yuan-Guo Tan, Xin Xin, Wen-Ru Sun. Distribution of Phosphorus and Its Effects on Precipitation Behaviors and Tensile Properties of IN718C Cast Superalloy[J]. Acta Metallurgica Sinica (English Letters), 2019, 32(7): 887-899.

图/表 15

Table 1 Analyzed contents (wt%) of P in the alloys

Alloy	1	2	3	4	5
P	0.001	0.015	0.022	0.025	0.035

Table 2 Heat treatment regimes

A	1095 °C/1.5 h WQ?+?955 °C/1 h WQ?+?720 °C/8 h ^107min620 °C/8 h WQ
B		1120 °C/10 h ^5min1160 °C/1 h ^5min 1190 °C/65 h

Fig. 1 Typical as-cast microstructures of IN718C alloys: a alloy 1; b alloy 5

Fig. 2 Microstructures of the alloys heat treated by the first stage of regime A, 1095 °C/1.5 h WQ: a alloy 1; b alloy 5

Fig. 3 Microstructures of the alloys with various P contents, heat treated by the first two stages of regime A, 1095 °C/1.5 h WQ?+?955 °C/1 h WQ: a alloy 1; b alloy 2; c alloy 3; d alloy 5

Fig. 4 Microstructures of the alloys with various P contents: a typical microstructure of the alloy heat treated by regime B?+?WQ; b alloy 1, regime B?+?WQ?+?955 °C/2 h WQ; c alloy 5, regime B?+?WQ?+?955 °C/2 h WQ

Fig. 5 Micro-hardness changes of the alloys with various P contents during treatment regime A

Fig. 6 Effect of P on tensile properties at room temperature of the alloys heat treated by regime A

Fig. 7 Fractographs of the alloys with various P contents: a alloy 1; b alloy 2; c alloy 3; d alloy 5

Fig. 8 Fractographs of the alloys with various P contents: a alloy 1; b alloy 2; c alloy 3; d alloy 5

Fig. 9 Longitudinal microstructures near the fractures: a alloy 1; b alloy 2; c alloy 3; d alloy 5

Fig. 10 Micro-hardnesses of the alloys with various P contents, heat treated by regime B followed by AC and WQ

Fig. 11 TEM images and corresponding SAED patterns with [001] zone axis: a alloy 1, WQ, bright-field image; b alloy 2, WQ, bright-field image; c alloy 5, WQ, bright-field image; d alloy 1, AC, bright-field image; e alloy 2, AC, dark-field image of γ″ and γ′ phases, (0 1 0) direction; f alloy 5, AC, dark-field image of γ″ and γ′ phases, (0 1 0) direction

Fig. 12 Micro-hardnesses and corresponding TEM microstructures of the alloys with various P contents treated by the regime B followed by water quenching and double aging

Fig. 13 Longitudinal microstructures of the tensile fracture surfaces: a alloy 1; b alloy 5

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