Science and Technology on Advanced High Temperature Structural Materials Laboratory, AEEC Beijing Institute of Aeronautical Materials, Beijing 100095, China
Cite this article:
FENG Yefei,ZHOU Xiaoming,ZOU Jinwen,WANG Chaoyuan,TIAN Gaofeng,SONG Xiaojun,ZENG Weihu. Interface Reaction Mechanism Between SiO2 and Matrix and Its Effect on the Deformation Behavior of Inclusionsin Powder Metallurgy Superalloy. Acta Metall Sin, 2019, 55(11): 1437-1447.
Powder metallurgy (P/M) Ni-based superalloy has been the most important material for high-temperature structural application in turbine disc owing to its good tensile and creep properties. However, the inclusions in P/M superalloy have an important impact on the safety and reliability of superalloy. By means of implanting SiO2 inclusions artificially, the evolution rule of morphology, size and chemical composition of 30 and 60 μm inclusions in FGH96 superalloy during powder, hot isostatic pressing (HIP) and hot extrusion (HEX) processes was investigated by SEM, EPMA, TEM, nanoindentation and Micro-CT. The interfacial reaction mechanism between inclusions and matrix alloy was revealed deeply, the size change of inclusions during different stages was studied quantitatively, and the 3D morphology of inclusions was characterized. The results show that the inclusions in powder stage are long stripe or plate-like shape, the displacement reaction happened in the process of HIP, which produced the composite inclusions with TiO2 inside and Al2O3 outside dispersed uniformly in the γ matrix, and the phase types of oxides were confirmed, furthermore, the reaction mechanism was figured out. Meanwhile, the denuded zone of γ' phase appeared around the inclusions with the dimension of 60 μm, but not 30 μm. The alloy matrix had higher elastic modulus and hardness than the denuded zone of γ' phase, implying that the denuded zone was softened zone. After the reaction, the dimension of inclusions became larger, the average size of 30 and 60 μm inclusions were 35 and 75 μm, respectively. During the HEX, owing to existence of the denuded zone, 60 μm inclusions had different deformation behaviors with 30 μm inclusions, and the dimension of inclusions obtained from statistics by SEM was used to contrast and validate with the results from formula calculation and Micro-CT.
Fig.1 SEM images and EDS (insets) of implanted SiO2 powder particles with the nominal dimensions of 30 μm (a) and 60 μm (b)
Fig.2 SEM images of implanted SiO2 with the nominal dimensions of 30 μm (a) and 60 μm (b) after hot isostatic pressing (HIP)Color online
Fig.3 SEM images and element distribution maps of EPMA of composite inclusions after HIP with nominal dimension of 30 μm (a) and 60 μm (b)Color online
Fig.4 Low (a, c) and high (b, d) magnified SEM images of 30 μm (a, b) and 60 μm (c, d) composite inclusions after HIP
Fig.5 Composition schematics of composite inclusions with the dimensions of 30 μm (a) and 60 μm (b)Color online
Fig.6 TEM images of composite inclusions with the dimension of 30 μm (a), SAED patterns (b, c) and EDS (d) of zone 1, SAED patterns (e, f) and EDS (g) of zone 2 in Fig.6a
Fig.7 Test distribution map of nanoindentation of complex inclusion with the dimension of 60 μmColor online
Zone
Nanohardness GPa
Elastic modulus / GPa
Denuded zone of γ' phase
7.2
125.4
Al2O3
37.2
315.0
TiO2
44.3
439.7
γ phase in inclusion
5.7
107.0
Matrix
16.9
213.0
Table 1 Micromechanical properties of different zones of 60 μm composite inclusions
Fig.8 SEM images of parallel to extrusion direction of inclusions in different locations of extruded billet (R—radius of extruded billet)(a~c) 30 μm inclusions, extrusion ratio is 6∶1 (d~f) 30 μm inclusions, extrusion ratio is 8∶1(g~i) 60 μm inclusions, extrusion ratio is 6∶1 (j~l) 60 μm inclusions, extrusion ratio is 8∶1
Fig.9 Schematic of shear deformation of inclusions during extrusion process (vx—alloy flow rate along x direction; τx—shear stress along x direction)
Fig.10 3D images of inclusions at different locations of extruded billet when extrusion ratio 6∶1 and 30 μm inclusion at 0.5R (a), 60 μm inclusion at the core (b), 0.5R (c) and rim (d) of extruded billet, respectivelyColor online
[1]
ZouJ W, WangW X. Development and application of P/M superalloy [J]. J. Aero. Mater., 2006, 26(3): 244
ShamblenC E, ChangD R. Effect of inclusions on LCF life of HIP plus heat treated powder metal René 95 [J]. Metall. Trans., 1985, 16B: 775
[6]
PateS J, ElliottI C. Production of high-strength P/M disc alloys by "superclean" cast/wrought technology [A]. Superalloys 1992 [C]. Warrendale: Minerals, Metals & Materials Society, 1992: 13
[7]
SimsC T, StoloffN S, HagelW C. Superalloys II: High-temperature Materials for Aerospace and Industrial Power [M]. New York: John Wiley & Sons Inc., 1987: 291
[8]
HuronE S, RothP G. The influence of inclusions on low cycle fatigue life in a P/M nickel-base disk superalloy [A]. Superalloys 1996 [C]. Hopeland: Minerals, Metals & Materials Society, 1996: 359
[9]
LaitinenA, H?nninenH. Effect of non-metallic inclusions on corrosion fatigue resistance of P/M duplex stainless steels [J]. Fatigue Fract. Eng. Mater. Struct., 1996, 19: 1045
[10]
de BussacA. Prediction of the competition between surface and internal fatigue crack initiation in PM Alloys [J]. Fatigue Fract. Eng. Mater. Struct., 1994, 17: 1319
[11]
AmbroiseM H, BretheauT, ZaouiA. Micromechanics and Inhomogeneity [M]. New York, NY: Springer, 1990: 41
[12]
GabbT P, TelesmanJ, KantzosP T, et al. Initial assessment of the effects of nonmetallic inclusions on fatigue life of powder-metallurgy-processed udimet 720 [R]. Washington: National Aeronautics and Space Administration, 2002: 7
[13]
ZhouX M, WangW X, YangH T, et al. Character of artificial non-metallic inclusions in HIPed FGH96 alloy [J]. J. Aeronaut. Mater., 2005, 25(4): 1
GuoW M, WuJ T, ZhangF G, et al. Characteristic of inclusions and its relationship with different forming processes in powder superalloy [J]. Mater. Rev., 2004, 18(11): 87
ZhangM C, FangS, ChenY H, et al. Deformation behavior of non-metallic inclusions of FGH96 alloy in extrusion process [J]. Forg. Stamp. Technol., 2013, 38(6): 132
KantzosP T, BarrieR, BonacuseP, et al. The effects of forging strain on ceramic inclusions in a disk superalloy [A]. Advanced Materials and Processes for Gas Turbines [C]. Warrendale, PA: TMS, 2003: 245
[18]
BonacuseP, TelesmanJ, KantzosP, et al. The effect of powder cleanliness on the fatigue behavior of powder metallurgy Ni-disk alloy Udimet 720 [A]. Proceedings of the 10th International Symposium on Superalloys: Technical Program & Calendar of Events [C]. Warrendale, PA: TMS, 2004: 409
[19]
BonacuseP J, KantzosP, TelesmanJ, et al. Modeling ceramic inclusions in powder metallurgy alloys [A]. Proceedings of the 8th International Fatigue Congress [C]. West Midlands: Engineering Materials Advisory Services, Ltd., 2002: 1339
[20]
McClungR C, EnrightM P, LiangW W. Integration of NASA-developed lifting for PM alloys into DARWIN [R]. Cleveland: NASA Glenn Research Center, 2011
[21]
JablonskiD A. The effect of ceramic inclusions on the low cycle fatigue life of low carbon astroloy subjected to hot isostatic pressing [J]. Mater. Sci. Eng., 1981, 48: 189
[22]
SimsC T, translated by ZhaoJ, ZhuS J, LiX G, et al. Superalloys [M]. Dalian: Dalian University of Technology Press, 1992: 124
