Effect of the Mold Positive and Negative Rotation on the Microstructure and Room-Temperature Mechanical Properties of K4169 Superalloy
CHEN Cheng1, YANG Guangyu1(), JIN Menghui1, WANG Qiang1, TANG Xin2, CHENG Huimin3, JIE Wanqi1
1 State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China 2 Key Laboratory of Advanced High Temperature Structural Materials, AECC Beijing Institute of Aeronautical Materials, Beijing 100095, China 3 Xi'an North Optoelectronics Technology Defense Co. Ltd., China North Industries Group Corporation Limited, Xi'an 710043, China
Cite this article:
CHEN Cheng, YANG Guangyu, JIN Menghui, WANG Qiang, TANG Xin, CHENG Huimin, JIE Wanqi. Effect of the Mold Positive and Negative Rotation on the Microstructure and Room-Temperature Mechanical Properties of K4169 Superalloy. Acta Metall Sin, 2024, 60(7): 926-936.
The service temperature of K4169 superalloy aeronautic turbine disks and other important aeronautic components is generally below the equi-strength temperature, and grain refinement can significantly improve the service performance. Compared with the conventional gravity casting process, the centrifugal casting process as a dynamic grain refinement method plays an important role in grain refinement, feeding, and molten filling of the casting. A precision casting with typical structural characteristics of the K4169 superalloy was prepared using the centrifugal casting process with the mold positive and negative rotation method and the conventional gravity casting process, respectively. The alloy microstructure, element segregation, secondary phase distribution, fracture microstructure, and mechanical properties at room temperature were compared and studied under two process conditions. The as-cast structure of the K4169 superalloy can be significantly refined using the mold positive and negative rotation method. The grain refinement of the experimental alloy was the most significant when the casting mold was reversed for 4 s, and the grain size under gravity casting decreased from (5.37 ± 0.21) mm to (0.27 ± 0.01) mm. Also, the primary phase of the experimental alloy was broken and the dendrite morphology was degraded that the coarse dendrites were replaced by broken dendrites and rose-shaped crystals after positive and negative rotations. Compared with unidirectional rotation, the segregation of alloying elements decreased, the number of Laves phases in the solidified structure was reduced, and the number of carbides was slightly increased. The tensile strength of the K4169 alloy at room temperature under the positive and negative rotation duration of 4 s was 31.4% higher than that under conventional gravity casting.
Fig.1 Dimension (unit: mm) (a) and schematic (b) of the tensile specimen
Fig.2 Microstructures of as-cast K4169 superalloy typical structural parts under different casting processes (a) conventional casting (CC) (b) positive and negative rotation (P&NR) for 4 s (P&NR 4s) (c) P&NR for 8 s (P&NR 8s)
Fig.3 Morphologies of the primary phase of as-cast K4169 superalloy typical structural parts under different processes (a) CC (b) P&NR 4s (c) P&NR 8s
Fig.4 Segregation coefficients of alloying elements in K4169 superalloy typical structural parts under different casting processes
Fig.5 XRD spectra of as-cast K4169 superalloy typical structural parts under different casting processes
Fig.6 Phases and its EDS analysis locations in the K4169 superalloy (a) bulk Laves phase (b) eutectic Laves phase (c) MC phase
Position in Fig.6
Al
Ti
Cr
Fe
Ni
Nb
Mo
C
1
0.28
0.84
13.76
9.71
36.36
31.18
7.87
0
2
0
3.90
8.18
8.10
50.34
22.16
7.32
0
3
0
8.24
0.61
0.59
1.13
68.87
0.18
20.38
Table 1 EDS analyses of phases in the K4169 alloy
Fig.7 Microhardness of matrix and different second phases in the as-cast K4169 superalloy
Fig.8 Distributions of Laves phase and carbides in as-cast K4169 superalloy typical structural parts under different casting processes (Insets are the corresponding locally magnified images) (a) CC (b) P&NR 4s (c) P&NR 8s
Fig.9 Area fractions of Laves phase and carbides in the structure of as-cast K4169 superalloy typical structural parts under different casting processes
Process
UTS / MPa
EL / %
CC
638.43 ± 10.36
19.76 ± 1.24
P&NR 4s
838.73 ± 3.49
29.83 ± 1.76
P&NR 8s
808.16 ± 10.60
20.63 ± 0.23
Table 2 Room-temperature tensile mechanical properties of body specimens in as-cast K4169 superalloy typical structural parts under different casting processes
Fig.10 Room-temperature tensile fracture morphologies of as-cast K4169 superalloy typical structural parts under diff-erent casting processes (a) CC (b) P&NR 4s (c) P&NR 8s
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