Effects of Phosphorus and Iron on Microstructures and Mechanical Properties in NiCrFe-Based Alloys

doi:10.1007/s40195-018-0784-7

Abstract

Abstract:

The microstructures and mechanical properties, especially creep properties, of the NiCrFe-based alloys with various contents of phosphorus and iron were investigated. The results showed that the tensile yield strength decreased with increasing iron contents while had no obvious change with the addition of phosphorus. For creep properties, the alloy with 15.8 wt% iron and 0.09 wt% phosphorus possessed the longest creep life (679 h) among all alloys. Only M₂₃C₆was formed in the alloys with low phosphorus contents, while both intergranular M₃P and M₂₃C₆ precipitated with the increment of phosphorus, which enhanced the strength of grain boundary by hindering the movements of dislocations during creep tests. The reasons for the enhancement of creep life were mainly related to the solid solution strengthening effect of phosphorus and optimization of grain boundary precipitations by phosphorus.

Key words: NiCrFe-based alloys, Phosphorus, Iron, Microstructures, Creep properties

Xin-Tong Lian, Wen-Ru Sun, Fang Liu, Dan-Dan Zheng, Xin Xin. Effects of Phosphorus and Iron on Microstructures and Mechanical Properties in NiCrFe-Based Alloys[J]. Acta Metallurgica Sinica (English Letters), 2019, 32(5): 659-667.

Figures/Tables 11

Table 1 Chemical compositions of different NiCrFe-based alloys (mass fraction, %)

	P	Cr	Fe	C	Ni
Alloy 1	0.025	17.17	15.2	0.039	Bal.
Alloy 2	0.09	17.42	15.8	0.041	Bal.
Alloy 3	0.025	17.11	30.5	0.044	Bal.
Alloy 4	0.09	17.32	30.1	0.040	Bal.

Fig. 1 As-heat-treated microstructure of NiCrFe-based alloys with different Fe and P additions: a alloy 1; b alloy 2; c alloy 3; d alloy 4

Table 2 Tensile properties of alloys at the temperature of 650 °C

Alloy No.	Alloy 1	Alloy 2	Alloy 3	Alloy 4
Yield strength (MPa)	302	297	239	220
Tensile strength (MPa)	416	407	393	384
Elongation (%)	64	61	56	55

Fig. 2 Creep curves of NiCrFe-based alloys with different P and Fe additions

Table 3 Creep rupture life and elongation of NiCrFe-based alloys at 650 °C with an initial stress of 150 MPa

Alloy No.	Alloy 1	Alloy 2	Alloy 3	Alloy 4
Life (h)	326	679	244	271
Elongation (%)	25	30	30	23

Fig. 3 Vickers hardness in the grain interior of alloys under different conditions

Fig. 4 Fractographs of the samples crept to rupture at 650 °C with an initial stress of 150 MPa: a, b alloy 1; c, d alloy 2; e, f alloy 3; g, h alloy 4

Fig. 5 Microstructure of alloys crept at 650 °C with an initial stress of 150 MPa and interrupted at 60 h: a alloy 1; b alloy 2; c alloy 3; d alloy 4

Fig. 6 TEM images, SAED patterns and EDS of the precipitates in alloy 2 crept for 60 h: a, cM3P; b, dM23C6

Fig. 7 Microstructures of the alloys crept to rupture at 650 °C with an initial stress of 150 MPa: a alloy 1; b alloy 2; c alloy 3; d alloy 4

Fig. 8 Dislocation patterns in alloy 2 crept for 60 h around aM23C6 and bM3P; TEM images at the same place of M3P c; grain boundaries d

References

[1]	C. Wang, H. Zhao, Y. Guo, J. Guo, L. Zhou, Mater. Res. Innov. 18, 325(2014)
[2]	L. Zheng, T.D. Xu, Q. Deng, J.X. Dong, Mater. Lett. 62, 55(2008)
[3]	W.R. Sun, S.R. Guo, J.T. Guo, D.Z. Lu, Z.Q. Hu, Acta Metall. Sin. (Engl. Lett.) 31, 349(1995)
[4]	W.R. Sun, S.R. Guo, D.Z. Lu, Z.Q. Hu, Met. Mater. Trans. A 28, 649 (1997)
[5]	S.L. Yang, W.R. Sun, J.X. Wang, Z.M. Ge, S.R. Guo, Z.Q. Hu, J. Mater. Sci.Technol. 27, 539(2011)
[6]	Z.Q. Hu, W.R. Sun, S.R. Guo, Acta Metall. Sin. (Engl. Lett.) 9, 443(1996)
[7]	S. Zhang, X. Xin, L.X. Yu, A.W. Zhang, W.R. Sun, X.F. Sun, Metall. Mater. Trans. A 47, 1 (2016)
[8]	S.R. Guo, W.R. Sun, D.Z. Lu, Z.Q. Hu, in Superalloys 718, 625, 706 and Various Derivativesed, ed. by E.A. Loria (TMS, Warrendale, 1997), p. 521
[9]	X.B. Liu, J.X. Dong, B. Tang, Y. Hu, X.S. Xie, Mater. Sci. Eng., A 270, 190 (1999)
[10]	C.G. McKamey, C.A. Carmichael, W.D. Cao, R.L. Kennedy, Scr. Mater. 38, 485(1998)
[11]	X. Liu, H. Liu, J. Dong, X. Xie, Scr. Mater. 42, 189(2006)
[12]	Z.Q. Hu, W.R. Sun, S.R. Guo, D.Z. Lu, Chin. J.Nonferrous Met. 11, 947(2001)
[13]	M.Q. Wang, J.H. Du, Q. Deng, Z.L. Tian, J. Zhu, Mater. Sci. Eng., A 626, 382 (2015)
[14]	L.X. Yu, Y.R. Sun, W.R. Sun, X.F. Sun, S.R. Guo, Z.Q. Hu, Mater. Sci. Eng., A 527, 911 (1998)
[15]	W.D. Cao, R.L. Kennedy, in Superalloys, ed. by R.D. Kissinger (TMS, Warrendale, 1996), p. 597
[16]	H.U. Hong, B.S. Rho, S.W. Nam, Mater. Sci. Eng., A 318, 292 (2001)
[17]	R.M. Wang, Y.G. Song, Y.F. Han, J. Alloys Compd. 311, 402(2000)
[18]	Q.Z. Chen, C.N. Jones, D.M. Knowles, Mater. Sci. Eng., A 385, 418 (2004)
[19]	S. Guan, C.Y. Cui, Y. Y, Y.F. Gu.Mater. Sci. Eng., A 662, 279 (2016)
[20]	T. Lin, Y. Guo, Z. Wang, H.P. Shao, H.Y. Lu, F.H. Li, X.B. He, Int. J. Refract. Met. Hard Mater. 72, 228(2018)
[21]	W.M. Gui, H.Y. Zhang, M. Yang, T. Jin, X.F. Sun, Q. Zheng, J. Alloys Compd. 695, 1272(2017)
[22]	W.M. Guo, Z.C. Wang, Y.D. Li, N. Xu, J.B. Shi, Metallogr. Microstruct. Anal. 2, 255(2013)
[23]	X.L. Song, Z.X. Yuan, J. Jia, D. Wang, L.X. Fan, Scr. Mater. 63, 448(2010)
[24]	H. Okamoto, Bull. Alloys Phase Diagr. 11, 405(1990)