Ablation Mechanism of Carbon/Carbon Composites Modified by HfC-SiC in Two Conditions Under Oxyacetylene Torch

doi:.10.1016/j.jmst.2016.01.013

Abstract

Abstract:

C/C-HfC-SiC composites prepared by precursor infiltration and pyrolysis process were ablated by oxyacetylene torch under two different flame conditions. The ablation performance of the composites was investigated in the heat flux of 2.38 MW/m² (HF-L) and 4.18 MW/m² (HF-H) for 60 s. The mechanical denudation in 4.18 MW/m² (HF-H) was higher than that in 2.38 MW/m² (HF-L), while the results indicated that the composites had a similar and good ablation property under two different flame conditions. C/C-HfC-SiC composites can adapt the heat flux from 2.38 MW/m² to 4.18 MW/m². The HfO₂ was not melted completely in the heat flux of 2.38 MW/m² (HF-L). So, both HfO₂ and SiO₂ layers acted as an effective barrier to the transfer of heat and oxidative gases into the underlying carbon substrate. SiO₂ was severely consumed in 4.18 MW/m² (HF-H), where the HfO₂ molten layer played a more important role in protecting the inner composite.

Key words: Carbon/carbon composites, Corrosion, Ablation performance

Li Ke-Zhi,Duan Tao,Zhang Jia-Ping,Liu Ning-Kun,Zhang Mao-Yan. Ablation Mechanism of Carbon/Carbon Composites Modified by HfC-SiC in Two Conditions Under Oxyacetylene Torch[J]. J. Mater. Sci. Technol., 2017, 33(1): 71-78.

Figures/Tables 10

Table 1 Ablation parameters of oxyacetylene flame

Specimens	Pressure (MPa)		Gas flux (L/s)		Heat flux (MW/m²)
Specimens	O₂	C₂H₂	O₂	C₂H₂	Heat flux (MW/m²)
F-L	0.4	0.095	0.24	0.18	2.38
HF-H	0.4	0.095	0.42	0.31	4.18

Fig.1 BSE images of cross-section (a-d) and XRD pattern (e) of prepared C/C-SiC-HfC composites

Fig.2 Surface appearance of C/C-HfC-SiC composites ablated for 60 s under different heat flux and the schematic diagram for dividing regions: (a) in HF-L, (b) in HF-H.

Fig.3 Linear ablation rate (a) and the maximum surface temperature (b) of prepared composites in the two heat fluxes

Fig.4 XRD patterns of prepared C/C-HfC-SiC composites after ablation in the two heat fluxes: (a) HF-L, (b) HF-H

Fig.5 Morphologies (a-e) and EDS analysis (f-h) in region A of specimens after ablation for 60 s in HF-L (see Fig. 2): (a) micrograph of area d; (b) micrograph of area e; (c) micrograph of area f; (d) and (e) micrographs of particles

Fig.6 Morphologies (a-e) and EDS analysis (f) in region A of specimens after ablation for 60 s in HF-H (see Fig. 2): (a) micrograph of area d, (b) high magnification of area E in (a); (c) micrograph of area e; (d) micrograph of area f; (e) high micrograph of particles

Fig.7 Morphologies (a, b) and EDS analysis (c, d) in region B of specimens after ablation for 60 s in HF-L (see Fig. 2)

Fig.8 Morphologies in region B of specimens after ablation for 60 s in HF-H (see Fig. 2)

Fig.9 Schematic diagram of ablation process

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