Microstructure and Property of MoSi2-30Al2O3 Electrothermal Coating Prepared by Atmospheric Plasma Spraying

doi:10.15541/jim20180394

Abstract

Abstract:

With MoSi₂-30Al₂O₃mixed powders as the raw material, MoSi₂-30Al₂O₃ electrothermal coating was sprayed by atmospheric plasma spraying technology. The phase composition, microstructure and thermal stability of the coating were systematically studied by XRD, SEM, electrical test and differential thermal gravity analysis. The results show that MoSi₂-30Al₂O₃ electrothermal coating shows dense microstructure. Al₂O₃ can improve the electrical resistivity and oxidation resistance of MoSi₂materials in low temperature. The coating exhibits an excellent electrical-heating performance. In the heating cycle test, it could be heated to 320 ℃ stably and exhibit uniform thermal distribution in the surface area. The temperature variation in roll’s central area can be controlled within 25 ℃; Oxidation and thermal stress relaxation during heating cycle would generate cracks and pores in the coating which would increase electrical resistivity.

Key words: electrothermal material, MoSi₂-Al₂O₃composite coating, atmospheric plasma spraying, electrical- heating performance

CLC Number:

TQ174

Yan-Zhe ZHOU, Min LIU, Kun YANG, Wei ZENG, Jin-Bing SONG, Chun-Ming DENG, Chang-Guang DENG. Microstructure and Property of MoSi₂-30Al₂O₃ Electrothermal Coating Prepared by Atmospheric Plasma Spraying[J]. Journal of Inorganic Materials, 2019, 34(6): 646-652.

Figures/Tables 13

Table 1 Atmospheric plasma spraying parameters

Sample	Current/A	Voltage/V	Distance/mm	Flux of Ar/(L?min^-1)	Flux of H₂/(L?min^-1)	Powder feed rate/(g?min^-1)
NiAl	600	70	110	45	8	20
MgAl₂O₄	630	75	110	40	11	19
MoSi-Al₂O₃	600	76	110	41	12	24

Fig. 1 XRD patterns of MoSi2-30Al2O3 powder and coating

Fig. 2 SEM images of MoSi2-30Al2O3 coating

Fig. 3 Polished cross-section morphologies of electrothermal coating system (a) and MoSi2-30Al2O3 coating (b, c); EDS analysis of corresponding points (1,2,3)

Fig. 4 Thermogravimetric (TG) curves of MoSi2-Al2O3 coating

Fig. 5 Thermogravimetric (TG) and differential scanning calorimeter (DSC) curves for MoSi2-30Al2O3 coating

Fig. 6 Photograph of ceramic heating roller (a) and infrared thermal image of the heating roller during insulation stage (b)

Fig. 7 Heating t-T curves of MoSi2-Al2O3 heating roller

Fig. 8 Cyclic heating t-T curve of MoSi2-30Al2O3 heating roller

Fig. 9 Relationship between resistivity of coating and heating time

Fig. 10 Relationship between resistivity of coating and temperature

Fig. 11 XRD pattern of MoSi2-30Al2O3 coating after 5 heating cycles

Fig. 12 Surface (a), cross-section (b) and fracture (c) morphologies of MoSi2-30Al2O3 coating after 5 cycles; EDS analysis of corresponding point (1)

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Microstructure and Property of MoSi₂-30Al₂O₃ Electrothermal Coating Prepared by Atmospheric Plasma Spraying

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