Tensile Creep Behavior of Cansas-II SiCf/SiC Composites at High Temperatures

doi:10.15541/jim20220441

Abstract

Abstract:

Continuous silicon carbide fiber reinforced silicon carbide composite (SiC_f/SiC) is a key material for the advanced aero-engines. It is required to possess excellent high-temperature creep resistance for SiC_f/SiC to meet the long-term service lifetime of the aero-engines. Here, tensile creep behaviors of a plain woven Cansas-II SiC_f/SiC (2D-SiC_f/SiC) were investiged in the temperature of 1200-1400 ℃ with the stress levels of 80 to 140 MPa. Its microstructure and fracture morphology were observed, and composition was analyzed. Results show that creep-rupture time of 2D-SiC_f/SiC is more than 500 h and steady-state creep rate is 1×10^-10-5×10^-10 /s at stresses lower than the proportional limit stress (σ_PLS). The creep behaviors are controlled by matrix and fibers. The creep-rupture time is significantly reduced, and the steady-state creep rate is increased by an order of magnitude when the stress is higher than the σ_PLS. The matrix, fibers and interfaces of the composite are greatly oxidized, and the creep behaviors are mainly controlled by the fibers.

Key words: Cansas-II SiC_f/SiC, creep, creep rupture time, steady-state creep rate, matrix cracking

CLC Number:

TB332

JING Kaikai, GUAN Haoyang, ZHU Siyu, ZHANG Chao, LIU Yongsheng, WANG Bo, WANG Jing, LI Mei, ZHANG Chengyu. Tensile Creep Behavior of Cansas-II SiC_f/SiC Composites at High Temperatures[J]. Journal of Inorganic Materials, 2023, 38(2): 177-183.

Figures/Tables 12

Table 1 Basic properties of domestic second-generation Cansas-II silicon carbide fibers

Diameter/ μm	Density/ (g·cm^-3)	Tensile strength/GPa	Tensile modulus/GPa
14	2.74	2.7	270

Table 2 Tensile properties of 2D-SiCf/SiC composites

Temperature/℃	E/GPa	σ_PLS/MPa	σ_UTS/MPa	ε/%
RT	273	115	282	0.57
1200	259	110	249	0.74
1300	223	92	229	0.60

Fig. 1 Dimensions and shape of tensile and tensile creep specimen (unit: mm)

Fig. 2 Tensile creep curves of 2D-SiCf/SiC at high temperatures (a) 1200 ℃, different stress; (b) 1300 ℃, different stress; (c) 1400 ℃, different stress; (d) Different temperatures, 100 MPa

Table 3 Tensile creep properties of 2D-SiCf/SiC composites in air at high temperatures

Specimen	Tempera- ture/℃	Stress/ MPa	Steady-state creep strain rate/s^-1	Creep rupture time/h	Creep strain/%
2D-SiC_f/SiC	1200	100	1.86×10^-10	>560	0.20
	1200	110	4.95×10^-10	>560	0.23
	1200	120	2.16×10^-9	42	0.18
	1200	140	8.45×10^-7	0.1	0.21
	1300	90	5.62×10^-10	>500	0.28
	1300	100	1.73×10^-9	70	0.20
	1300	120	1.86×10^-8	6	0.28
	1400	80	1.32×10^-9	88	0.33
	1400	100	1.46×10^-8	1.6	0.57
CVI-SiC_f/SiC^[13]	1300	75	2.3×10^-9	111.1	—
	1300	90	6.2×10^-8	33.4	—
	1300	120	3.6×10^-7	0.83	—
	1300	150	3.0×10^-6	0.14	—
MI-SiC_f/SiC^[15]	1204	125	3.0×10^-11	>1000	0.25
	1204	140	2.3×10^-10	>1000	0.31
	1204	150	—	82.1	0.29

Fig. 3 Tensile stress-strain curves of as-received and crept 2D-SiCf/SiC

Table 4 Residual tensile properties of 2D-SiCf/SiC after creeping

		σ_UTS/MPa	E/GPa	σ_PLS/MPa	ε/%
As-received		282	273	115	0.57
Crept	1200 ℃/100 MPa	211	—	—	—
	1200 ℃/110 MPa	173	209	89	0.25
	1300 ℃/90 MPa	138	157	55	0.17

Fig. 4 Macroscopic morphologies of fractures of 2D-SiCf/SiC under different conditions (a) As-received; (b) Crept at 1200 ℃/110 MPa for 560 h; (c) Crept at 1200 ℃/120 MPa; (d) Crept at 1200 ℃/140 MPa

Fig. 5 Morphologies of fracture oxidation zone of 2D-SiCf/SiC under different creep rupture conditions (a) 1200 ℃/120 MPa; (b) 1300 ℃/100 MPa; (c) 1400 ℃/80 MPa

Fig. 6 Interface and fiber damage in 2D-SiCf/SiC during creeping at 1300 ℃/100 MPa (a) SiO2 filled; (b) SiO2 unfilled

Fig. 7 Longitudinal fiber microstructures of 2D-SiCf/SiC after crept (a)1200 ℃/110 MPa for 560 h; (b)1300 ℃/90 MPa for 500 h

Fig. 8 Larson-Miller plots for 2D-SiCf/SiC

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