High temperature oxidation and microstructure of MoSi2/MoB composite coating for Mo substrate |
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Affiliation: | 1. Hunan Provincial Key Defense Laboratory of High Temperature Wear-resisting Materials and Preparation Technology, Hunan University of Science and Technology, Xiangtan 411201, China;2. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;3. Key Laboratory of Ministry of Education for Non-ferrous Materials Science and Engineering, Central South University, Changsha 410083, China;4. Key Laboratory of Hunan Province for Metallurgy and Material Processing of Rare Metals, Central South University, Changsha 410083, China;5. School of Materials Science and Engineering, Central South University, Changsha 410083, China;1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;2. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, China |
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Abstract: | The two-layer MoSi2/MoB composite coatings were developed using the halide activated pack cementation (HAPC) method on Mo substrate. Oxidation resistance property and microstructural evolution of the coatings at high temperatures were investigated. During oxidation exposure, the coatings exhibited a good oxidation resistance property. The mass gains of the coated specimens oxidized at 1200 °C for 100 h and at 1300 °C for 80 h were 0.270 and 0.499 mg/cm2, respectively. Compared with the monolithic MoSi2 coatings, the transformation of MoSi2 phase in the MoSi2/MoB composite coatings was more sluggish at elevated temperatures. The growth rate constant of the Mo5Si3 layer in the composite coatings was two orders of magnitude lower than that of the Mo5Si3 layer in the monolithic coatings at 1300 °C. The microstructural degradation of MoSi2 in the composite coatings at high temperatures was slowed by the introduced MoB layer. The MoB layer in the composite coatings is useful to prolong the service life of MoSi2 coatings at high temperatures. |
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