Pyrolysis Behavior and Laser Ablation Resistance of PCS in Polycarbosilane Composite Coatings

doi:10.15541/jim20230143

Abstract

Abstract:

For the development of high-performance laser protective coatings, this work innovatively proposes the idea of recombining PCS ablative coatings on the surface of traditional yttrium stabilized zirconia (YSZ) thermal insulation coatings. Based on characteristics of the consumption of large amount laser energy through decomposition of polycarbosilane (PCS) and production of high-temperature ceramic protective phases, NiCrAlY/YSZ/PCS-TiO₂(YPT) and NiCrAlY/YSZ/PCS-Y₂O₃(YPY) coatings were prepared on the surface of Ni-based alloy by slurry method combined with atmospheric plasma spraying (APS). Based on the effect of TiO₂ and Y₂O₃ addition on the pyrolysis behavior of PCS, the laser ablation resistance of YPT and YPY composite coatings on 10.6 μm CO₂ laser were systematically studied and compared with that of single layer YSZ coating. The results show that YPY and YPT composite coatings have better laser protection effect than traditional YSZ coating, because in the early stage of laser ablation, the PCS decomposition on the coating surface can consume laser energy, and the residual Y₂SiO₅, SiC and SiO₂ phases after ablation can be deposited on the YSZ coating, forming a dense protective layer, which can continue to play a role in laser protection of the YSZ coating. YPY coating has better laser protection performance than YPT coating, because Y₂O₃ has higher thermal conductivity and lower coefficient of thermal expansion. Smaller temperature gradient can be produced in YPY coating, which can alleviate thermal stress. Moreover, Y₂O₃ participates in the pyrolysis of PCS to generate Y₂SiO₅ phase, which inhibits more volume expansion in PCS pyrolysis than that in TiO₂. In addition, the core ablation temperature of YPY coating is higher, and the formation of PCS pyrolysis products SiC and SiO₂ phase is faster, which can timely protect the lower coating, showing better laser ablation resistance. This study is expected to provide a new idea for the design of novel laser resistant composite coatings.

Key words: polycarbosilane, addition, composite coating, pyrolysis, laser ablation resistance

CLC Number:

TQ174

CAI Jia, ZHAO Fangxia, FAN Dong, HUANG Liping, NIU Yaran, ZHENG Xuebin, ZHANG Zhenzhong. Pyrolysis Behavior and Laser Ablation Resistance of PCS in Polycarbosilane Composite Coatings[J]. Journal of Inorganic Materials, 2023, 38(11): 1271-1280.

Figures/Tables 15

Table 1 Spray parameters of YSZ and NiCrAlY coatings[18]

Coatings	YSZ	NiCrAlY
Ar/slpm	30−40	30−40
H₂/slpm	5−15	5−15
Spray distance/mm	90−130	200−300
Feed rate/(r·min^-1)	15−30	15−30
Power/kW	38−48	30−40

Fig. 1 Schematic of 10.6 μm CO2 laser examination device

Fig. 2 XRD patterns of PT (a) and PY (b) coatings

Fig. 3 Infrared spectra of products pyrolyzed from PT (a) and PY (b) coatings at different temperatures

Fig. 4 TG (a) and DSC (b) curves of PT, PY and PCS

Fig. 5 XRD patterns of PT (a) and PY (b) coatings after heat-treated at different temperatures in air for 2 h

Fig. 6 Morphologies of YPT and YPY coatings ablated by 425 W/cm2 laser for different periods

Fig. 7 Temperature curves of YPT (a) and YPY (b) coatings ablated by 425 W/cm2 laser for different periods

Fig. 8 XRD patterns of YPT (a) and YPY (b) coatings after 425 W/cm2 laser ablation for different periods

Fig. 9 Surface SEM morphologies of YPT and YPY coatings after 425 W/cm2, 5 s laser ablation (a, d) Original morphologies; (b, e) Central ablative zone; (c, f) Transition zone; (g) EDS results of A1, A2 and P1 points

Fig. 10 Cross-sectional original SEM morphologies (a, d), cross-sectional morphologies (b, c, e, f) and EDS results (g, h) of YPT and YPY coatings after 425 W/cm2, 5 s laser ablation

Fig. 11 Surface morphologies (a) and back surface morphologies (b) of YSZ, YPT and YPY coatings ablated by 2123 and 4246 W/cm2 laser for 5 and 10 s, respectively

Fig. 12 XRD patterns of YPT (a) and YPY (b) coatings after 4246 W/cm2, 10 s laser ablation

Fig. 13 SEM surface morphologies and EDS analyses of YSZ, YPT and YPY coatingsafter 4246 W/cm2, 10 s laser ablation (a, e, i) Original coatings; (b, f, j) High magnification of central ablation areas; (c, g, k) Low magnification of central ablation areas; (d, h, l) Transition areas; (m) EDS results; (n) YPT element mappings ; (o) YPY element mappings

Fig. 14 Cross-sectional SEM morphologies and corresponding elements mapping of the central ablation area of YSZ (a), YPT (b) and YPY (c) coatings after 4246 W/cm2, 10 s laser ablation

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